105mm, 155mm or Something In-between?

A guest post from Obsvr

The defining characteristic of field artillery for the last century has been ‘firepower mobility’ of indirect fire.

Any target within range can be engaged, providing the effective command and control arrangements are in place.

This gives each battery a very large area of influence.

Many widely separate batteries can engage the same target or several targets simultaneously in the same area.

This mobile firepower is used to deliver weapons (the shell is the weapon of artillery) to suppress, cause casualties and damage, and if precision guided munitions are used, destroy.

Suppression is generally caused by the explosion, the size of the explosion is of no great consequence and the number required per unit of area per unit of time is modest, but time could be lengthy if dismounted infantry are being supported.

Casualties and damage are caused by shell fragments.

Fragments weighing less than a gram are lethal because of their high velocity, large fragments from a burst within about 10 metres of a lightly armoured vehicle may penetrate and fragments far further from a burst will damage optics, antennae and other external fittings of armoured fighting vehicles, tyres are likely to suffer significantly.

The probability of a fragment hit depends on fragment density which decreases with distance from the burst.

Crudely, the number of fragments is a function of shell size and the amount of HE.

For good fragmentation around 25% or more by weight of HE is required.

This threshold was first achieved in the 1970s by the UK designed 155mm L15 shell (45kg with over 11kg of HE).

The new 105mm L50 shell (15kg with just under 3kg) is better than most but still inferior to L15.

The distance from a burst at which there is a 50% chance of a person in the fragmentation zone  being hit by a groundburst fragment is about 30 metres for L50 and 55 metres L15, this increases a bit for 105mm airburst and lot for 155mm airburst.  The shape and area of this zone depend on the height of burst and angle of descent.

It is important to note that multi-function fuzes are now standard in some western armies, including the UK, giving choices of proximity height of burst, point detonating or delay.

There is an important reverse side to this coin, safe distances for own troops will be greater with 155mm than 105mm and this can be particularly significant when suppressive fire is being delivered to cover assaulting troops.

While bigger is better for damage and casualties, smaller is better for suppression.

The risks to own troops can be significantly reduced by using delayed action fuzes (providing the ground is suitable).

Course Correcting Fuzes would reduce the risks still further.

Course Correcting Fuse
Course Correcting Fuze

Another factor favouring 155mm is exotic cargo munitions such as electronic jamming payloads, SADARM sub-munitions able to destroy AFVs, even moving ones, and anti-armour mines.

155mm Ballistic Sensor Fuzed Munition
155mm Ballistic Sensor Fuzed Munition

105mm is adequate for more traditional natures such as smoke and illuminating.

Next consideration is rate of fire where it is impossible to beat self-propelled guns with a useful degree of automation.

The first point to note is that most casualties occur in the first 10 seconds. The modern availability of an airburst fuze with every round may alter this unless the target has immediate access to overhead protection. Guns like AS90 deliver 3 rounds in 10 seconds, FH70, a towed 155mm, achieved 3 in 15 seconds (like AS90 it had a primer magazine) and a towed 105mm won’t improve much on this.


The 155mm M777, lacking a primer magazine and relying on manual shell ramming seems to be about 2 rounds in 15 seconds.

On-board ammunition in SPs is limited, particularly if there are several ammunition types.

This makes ease and speed  of getting ammunition into the gun an important consideration.

Tracked SPs are best because, providing they have a rear hull door,  their floors are lower to the ground hence ammunition handling is quicker and easier.

British troops of D Battery, 3 Royal Horse Artillery, fire on enemy positions in Basra.  28 March 2003 Location: Iraq OP TELIC
British troops of D Battery, 3 Royal Horse Artillery, fire on enemy positions in Basra. 28 March 2003 Location: Iraq OP TELIC

Tracks are also less likely to be damaged than tyred wheels if a battery receives counter-battery fire.

The modern trend for wheeled artillery is a reminder of an artillery maxim, all too frequently forgotten, that ‘in peace the cry is for mobility, in war for weight of shell’.

This problem is a consequence of peacetime training where ammunition is limited and its real effects are not apparent, but there is a lot of scope for impressive rushing around.

In reality guns’ cross country mobility is limited by their loaded ammunition vehicles.

DROPS (Image Credit  - Plain Military)
DROPS (Image Credit – Plain Military)

Fortunately, built-up areas are well endowed with suitable gun positions and in most parts of the world there is seldom a need to deploy too far from solid surfaces. Nevertheless ‘into action time’ is a relevant issue, and if it is really fast it means that batteries can quickly respond to calls for fire when on the move.

Generally, towed 105mm will be faster than 155mm but spadeless self-propelled guns will always be the fastest, not least because they have ammunition onboard and ready to fire.

One final issue, traverse.

In conventional operations most targets can be engaged with an arc of fire of about 90 degrees.

Typically towed guns have top-traverse (ie saddle on carriage) of about 30 degrees left and right although M777 is limited to 23 degrees.

Targets outside the top traverse arc require the carriage to be man-handled, this takes time and delays the response to a call for fire, by some minutes with 155mm.

The M777 155mm howitzer
The M777 155mm howitzer


This is not a problem with turreted SP’s, nor is it an issue of any significance with a well balanced gun with a box-trail and platform.

These were introduced in 1918, later used with 25-pr and today with L118, but is probably impractical with 155mm.

All Terrain Mobility Platform 1 (ATMP) towing a Light Gun
All Terrain Mobility Platform 1 (ATMP) towing a Light Gun


But it is not clear that it has ever been tried, although sole plates have been used and undoubtedly facilitate wide traversing.

If there is a real need for movement by helicopter then towed guns are the only option and they need to be light.

If any sort of air movement is required then the lighter the gun the better.

Merlin Helicopter Light Gun Royal Artillery
Merlin Helicopter Light Gun Royal Artillery

It is useful to remember that L118 with essential stores and camouflage is about the same weight as two ammunition pallets (72 rounds) or about a hundred unboxed rounds.

Logistically, a given delivery weight will provide about twice as many packed  105mm shells as 155mm, although stripped of pallets, ULCs and boxes (leaving fibreboard tubes and plastic containers) it increases because 105mm uses more packaging.

From an effects perspective, 105mm is more efficient than 155mm for suppression.

For casualties and damage 155mm is probably three or more times as effective as 105mm.

For benchmark rates of fire (to inflict maximum casualties) a self-propelled gun with extensive automation is required. Importantly, the longer range of 155mm gives a greater area of influence than 105mm and places more batteries in range of a target area.

If the situation is counter-insurgency, then speed of all round traverse becomes an issue, the pecking order is simple, turreted SPs are best, then box-trail and platform, lastly anything else.

So, which is best, the only answer is ‘it depends on what you want’.

155mm gives the best coverage and lethality but 105mm is logistically more efficient for suppression and more suited to air movement and associated ammunition supply.

What about something that combines the qualities of both?

The problem here is that neither 105mm nor 155mm are particularly suitable as general purpose non-armoured artillery.

That suggests it’s time to think about alternatives.

Both came about because they were what the US used in WW2 and NATO decided to ‘standardise’ on them.

This 1950s standardisation was nonsense, there was no agreement of any characteristics except calibre, and a few years later the UK adopted their own standard of 105mm  which was a considerable improvement on what the US had been using, albeit with totally different ballistic characteristics.

Subsequently, there was ballistic standardisation agreed by a handful of nations for 155mm with 39 and 52 calibre length barrels.

The basic requirements are, perhaps, the best possible maximum range, a gun weighing no more than M777’s 3400 kg, but with rapid traversing over a large arc.

To keep ammunition weight down it should not use a metal cartridge case, so a sliding block breach with a primer magazine is required with the goal of 3 rounds in no more than 12 seconds.

The technology for this only exists in UK and Germany, although France produced a primer magazine for the 155mm AUF2.

Splitting the difference between 155mm and 105mm gives 130 mm and seems a good starting point.

The Soviet 130mm M46 was a WW2 vintage gun, reputedly naval in origin.

At some 8.5 tonnes it was distinctly ‘chunky’ and had a very long 55 calibre barrel with a high maximum muzzle velocity of some 930 m/s giving a maximum range of 27 km.

M46 130mm
M46 130mm


Projectiles were about 33kg, a tad more than the 105 – 155 midpoint of 30kg.

Rate of fire is usually given as up to 8 rds/min but this gun was not capable of high angle fire and its top traverse was only slightly better than M777.

Nevertheless, being designed some 70 years ago it provides food for thought.

Dropping down we reach 127mm, taking us back a century to the even older the 60-pr.

60 pounder Cape Helles June 1915.jpg. A 60-pounder Mk I at full recoil
60 pounder Cape Helles June 1915.jpg. A 60-pounder Mk I at full recoil

With a 37 calibre barrel this delivered various shells between 54 and 60 lbs (27 kg) using 4 kg propelling charge with a MV of 650 m/s to about 14 km.

Maximum elevation was limited to 37 degrees.

For comparison, a 5 inch (127mm) naval gun with a 38 calibre barrel, firing 25 kg shells with an MV of 790 m/s gave a range of almost 16 km. The 55 calibre version, with an MV of about 805 m/s gives 24 km range.

Finally 122mm with a 22kg shell.

The M1931 Gun, MV 800 m/s and 46 calibre barrel gave 20.4 km albeit with a total weight of 7900 kg, the M1955 (D74) was a considerable improvement, 5500 kg, 900 m/s MV, 47 calibre barrel and 23.9 km.

D30 weighing 3,200 kg with a 35 calibre barrel and MV 690 m/s gives 15.3 km.

It might be a politically astute move to adopt 122mm as a NATO calibre and in recognition of the newer members.

D30 Howitzer
D30 Howitzer


122mm is 48 lines in pre-1917 terms, ie 4.8 inches.

For comparison, 39 calibre 155mm has an MV of about 820 m/s for 24 km range and 105mm L118 with 37 calibre length, MV 810m/s gives 17.2 km

From this it seems reasonable to seek an ordnance of about 125mm, 40+ calibres, 800+ m/s MV firing 25 kg projectiles (with 5 – 6 kg of HE) to 20+ km with an in-action weight no more than M777.

The tricky bit is the carriage, with the need for rapid and wide traverse as well as the usual high angle fire and direct fire capabilities.

The basic requirement for such a carriage is to provide stability, this requires trails or stabilisers and the longer they are the greater the overall weight.  Trail length is determined by the recoil forces and the height of the trunnions. Minimising this height requires the trunnions to be as far back on the ordnance as possible (or severely limiting maximum elevation).

The shortest trail is a single pole trail, the problem is that this limits maximum elevation because it is in the way of the recoiling breach.  Split trails are the most common, but they have to be far apart to permit wide top traverse, and the wider the open trail angle the longer and hence heavier the trails need to be – this explains M777’s relatively short stabilisers and limited top traverse.

Lifting a pair of long and heavy trails, particularly when the spades at their ends have’ dug- in’ with firing, is never quick and not always easy.  The need is a carriage or mounting that can be quickly traversed over a large arc of fire.

Guns like the 122mm D30 that can traverse 360 degrees on its three legged mounting (a mounting because the wheels are not on the ground when firing) have long legs, they’re 120 degrees apart.

This configuration has another constraint, barrel elevation angle and hence range are limited whenever the barrel partially aligns with a leg, there is only some 48 degrees of full elevation traverse between each pair of legs.

Clearly this is not a suitable design.

The obvious solution is a box trail, as used with 25-pr and L118, or sole plate.

The latter requires lowering the sole plate to lift the wheels clear of the ground and still requires the trails to be lifted for a wide traverse.

The former rotates on its platform but invites the question as to whether it is doable with a gun of 3000+ kg or so.

The key to this is the balance of the gun so that once the trail is lifted the load is equally distributed forward and rear of the wheels, trunnions well to the rear facilitates this.

The ease of lifting the trail to the position of balance for a 3000+kg gun may still be a challenge. 

As an indication of the problem, the L119 has a shorter barrel than L118, it has a notably heavier muzzle brake to provide the necessary balance.

In summary, what is currently missing is a towed gun, light enough for tactical air movement, offering a wide and rapid arc of fire, and delivering a shell with a significant improvement over 105mm. 

155mm is not the solution. 

Something like 125mm seems reasonable but 122mm might be politically attractive although the existing 122mm ammunition would need much improvement


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July 9, 2014 5:26 pm

: might the tendency for guided ammunition and the consequent reduction in usage drive us towards 155mm? Or even rocket artillery? After all, if you can identify positions via a FOO, you don’t need to suppress, you can merely destroy at the opportune moment, while the close support role could become more a function of mortar platoons

Slightly Agricultural
Slightly Agricultural
July 9, 2014 5:28 pm

Very informative guest article Obsvr. And you’ve approached it absolutely the right way (for any projectile weapon) – what effect do you want, and on what target?

Most people pick their favoured calibre and go from there. Which is not helped when BAE keep slipping the brochure for M777 under the door at Larkhill and waggling their eyebrows sugestively…

Although whether they can reasonably tool up Glascoed for the calibre may be a bit of a showstopper for any new platform. (Or a great opportunity to flog …ahem…’export’… some quality new ammo natures, depending on any established user base!)

July 9, 2014 5:32 pm

It has been my experience that if you want “Immediate Suppression” that mortars in the 107-120mm class are the first/best choice at battalion level. If they are carrier-mounted and autoloading, so much the better. (I’ve grown fond of the NEMO turreted system through recent research.)

For deeper suppression fire missions, why couldn’t a future towed artillery system bigger than 105mm use a 4-leg stabilizer system like the WW2 German “eighty-eight” with 360° traverse?

July 9, 2014 5:34 pm

How about the naval 5 inch after all if we are fitting it our ships…….

July 9, 2014 5:41 pm

“If there is a real need for movement by helicopter then towed guns are the only option and they need to be light.”

Once again the ghost of ’82 comes to mind, helicopters were too busy shifting artillery and logistics (along with the loss of assets from Conveyor) which led to the tab and yomp of epic proportions and the subsequent impact on troops state.

I rather like the AS90 though, looks the job.
But I fear the job of replacing our pieces, all of which are inconveniently approaching the need for update/replacing, will be yet another shoestring or “planned but not budgeted for” thing :(

July 9, 2014 5:44 pm

Forgot to add, good post :)

Indeed, mentioning how our tracked AS90’s are only as mobile as their logistics trucks was something I failed to notice.

July 9, 2014 5:54 pm

Very good post. Very interesting and informative.

What level of ammunition consumption do we plan for?

July 9, 2014 6:35 pm

What a great opportunity to become a bit less uneducated! A v good article.

Following on from wf, the first contribution, the more sparsely populated /held battlefield requires more range. If you combine that with the option for precision munitions, 155mm gets a plus, rocketry gets two plusses, but has pityful reload times, balanced with extended range and precision.

Thereby I go with Kent, that for instant response, there will need to be man- carried 60-81 mm mortars and 120mm (breach loaded or not) mounted on the same type of vehicle that the infantry rides in. So a variation on the Stryker Fire Support vehicle, just not the only Jack in the card deck (this time, as opposed to the independently operating fast-wheeled concept brigade).

That’s three sizes plus what ever siuze the rockets take; as we know, same launcher units can handle different pods.

July 9, 2014 6:40 pm

With the (too) drastic cut of AS90, why was this not solved by turning the extra units into supply vehicles?
“Indeed, mentioning how our tracked AS90′s are only as mobile as their logistics trucks was something I failed to notice.” from Mike’s comment

July 9, 2014 6:50 pm

What I find interesting is the premise that the mid point of the 105 and 155mm would have the best of both worlds but the weaknesses of neither. Is this a viable presumption?

Phil, not sure about consumption rates, but IIRC someone here mentioned a rule of thumb that seems quite reliable in that SPGs carry one round per ton on average more or less, so the AS90 would be carrying 45+/- rounds for the whole op until resupplied. Assuming that planning is for a 3 day mission which is common, you get 15 rounds per day usage. This isn’t as bad as it sounds as a whole battery firing at once doesn’t need to use that many rounds per vehicle to flatten a target.

July 9, 2014 6:53 pm

If we went with the 5 inch, that is one piece ammunition. Less powder options but easier to transport.

July 9, 2014 6:56 pm

How well does the chally2s L30 do indirect fire? could we do a 120mm field gun so that the sheared ammo.

The Other Chris
July 9, 2014 6:57 pm

127mm gives commonality with the shiny new Mk 45 Mod 4’s…

July 9, 2014 7:05 pm

“With the (too) drastic cut of AS90, why was this not solved by turning the extra units into supply vehicles?
“Indeed, mentioning how our tracked AS90′s are only as mobile as their logistics trucks was something I failed to notice.” from Mike’s comment”

Presumably due to cost implications (DROPS vehicles are quite cheap) and the fact that – from my understanding at least – DROPS is extremely well liked throughout the entire logistics train especially in terms of moving large amounts of material with as little ‘slow’ manual handling as possible.

I will be happy to stand corrected of course.

Red Trousers
Red Trousers
July 9, 2014 7:16 pm

Excellent, Obsvr. Quite took me back to the 80s/90s in Germany and similar (my comfort zone ;) ).

I know I always joke about Gunners marrying cast off Cavalry Norland girlfriends, but a decent FOO is worth his weight in compo. I had the great fortune to have one of the cream of the crop when I had my Squadron. He like me was a maths monster and we did all sorts of mental balancing of various factors to come up with the best fire plan (his BC at RHQ was also a great contributor). It always started with me deciding on the effect I wanted to achieve, then we’d work out trajectories and ideal time on target, and he’d sort out the details and just basically organise it.

The only time we had to compromise from the ideal was with urban areas, where both tall buildings and later on ROE restrictions added further complications.

July 9, 2014 7:18 pm

– Sometimes “weight of throw” is most important. I’ve had the privilege of seeing the results of a M109A3155mm “battalion four” converged sheaf fire mission. Impressive to say the least.

July 9, 2014 7:30 pm

Very much recommended:

“The shape and area of this zone depend on the height of burst and angle of descent.”
he provides some nice info on this

“This is not a problem with turreted SP’s, nor is it an issue of any significance with a well balanced gun with a box-trail and platform.”

You still need to raise and set in the spade when you traverse a lot (in 25pdr-like platforms, not the siege artillery with huge diameter platforms).

“For casualties and damage 155mm is probably three or more times as effective as 105mm.”

Per shot maybe, and possibly even per MRSI (at certain ranges) but not in “per mass” or “per minute”.

July 9, 2014 8:04 pm

This might be a completely stupid suggestion, but

Could we standardise on 155 and fire 105s with a sabot? Would there be any advantage to doing so?

And now the really stupid question, could we fire more than one shell at once?
A 255 barrel can fit 4×105 shells.
Could we case them and fire them at once?

July 9, 2014 9:22 pm

Some other options:

1. Adopt more effective 105mm rounds and/or guns. The pre-formed fragment, M2020 105mm round claims to be more “lethal” than the M795 and M107 155mm rounds. The Denel Leo 105mm gun has a range of 30km.

2. Adopt a “smaller than MLRS” semi-precision rocket system. The Israeli LAR/ACCULAR is an obvious candidate. Reload time stinks but it can fire off its ready load faster than any gun system. The IAI Jumper is like NLOS-LS lite. It has a range of 50km with GPS/INS/SAL guidance.

3. Artillery is having greater degrees of difficulty, these days, deconflicting with airpower. Perhaps, instead of spending a lot more money on it, we should develop smaller, “dense-pack” munitions for aircraft and use them as flying artillery. The AC-130 is an obvious example of this, but suffers from survivability issues and cost.

There are various small, guided munition programs underway to enhance its ability to deliver fires from safer altitudes and ranges (e.g. Viper Strike, Griffin).

How about developing an air-dropped, GPS/INS-guided, 120mm mortar round that can be packed 15-or-so per BRU-61-sized rack? There has already been work done to build an 81mm air-dropped, guided mortar round and the groundwork appears to be there for a 120mm variant. This munition could be carried by any tactical aircraft or “bomber-of-opportunity” with BRU-61-rated hardpoints.

105mm PGK fuzes might allow an AC-130 to stand off much further away, and at much higher altitudes, while still delivering accurate fires.

July 9, 2014 9:46 pm

3. continued. Develop a GPS/INS version of APKWS. An aircraft carrying multiple 19-tube launchers could orbit near the fires zone. When the pilot gets a call for fires, he/she downloads the coordinates to as many rounds as needed, points the aircraft’s nose in the general direction for a ballistic trajectory and fires them off. The guidance does the rest.

July 9, 2014 10:15 pm

105mm is good if you close in and so is your target, but honestly in today’s environment the 155mm is even lacking the punch it needs. The 105mm of today is like the 75mm of WW2 and the 155mm of today is like the 105mm of the WW2 era. Where do we go from here? 155mm rounds have improved greatly but still have a way to go, only to be restricted by their size of 155 mm. Fuzes and other improvements have upgraded the munitions, but have we maxed out? I do not like the 130mm D30 field gun, They are and always will be crap. MLRS was supposed to have made the towed field gun obsolete, but did it really? Self Propelled is the way to go now and I really like the German PhZ2000 and the Swedish or South African Guns. The M109 Paladin is old and has no more room for upgrades. My career was as an Artilleryman, so I can only hope that the King of Battle in the future can still protect his queen (infantry).

Your Cousin from across the pond……

Swimming Trunks
Swimming Trunks
July 9, 2014 10:31 pm

@ Obsvr – an excellent and informative post. Before reading it my first thought was a 120mm gun, similar to the Russian 122mm. This might allow some commonality with tank rounds (shells rather than propellants); similar to the possible benefits of a 127mm weapon (Volcano rounds a possibility?) However, I feel Observer has a point – is this another weapon system triangulated between 105mm and 155mm or a single system to replace one or both of the old systems?

I recently read an article on the idea of replacing 60mm, 81mm and 120mm mortars with 60mm and 98mm ones:


RE: tracked SPH and resupply trucks – why not go for wheeled SPH? This article suggests 8×8 makes the most sense as a chassis for artillery, etc:

“The medium family might consist of only one basic wheeled platform (8 x 8) whose different variants (weighing 25 – 35 t) would carry heavy tube artillery, a multiple-launch rocket system, and/or a fiber-optically guided missile array. Its main function would be n), of course. In performing this function it would assist in a), g), k) as well as in follow-on forces attack and in stopping enemy breakthroughs. Emphasis would be placed on ensuring optimal fire allocation, which requires good operational mobility.”


July 9, 2014 11:57 pm

The failure to develop and procure a specialist resupply vehicle for AS90 was especially poor, but these things happen.

155mm is ultimately the future, you won’t get anything other than that or 105mm so discussing anything else is redundant anyway.

I rather link DONAR and the bonus is we could fit it to a modified scout platform (the prototype was on an ASCOD 2 modified)- would make for an interesting capability. That said, replacing a 155mm self propelled with a 155mm self propelled is a difficult sell in these straightened times when there are other far more whizz-bang things demanding money.

July 10, 2014 4:04 am

Well I don’t doubt the utility of the suggestion I think it makes zero sense. Giving up the 155 would lead us on to yet another bespoke UK only development path and cut us off from the wealth of future munitions being developed by the USA.

We would end up spending large amount’s of money or what is today a fairly niche capability. The M777 is probably the only real solution for replacing the 105 and the higher degree of precision should off set the need fro smaller rounds for suppression fire.

There is nothing wrong with the AS90 and we should keep it in service for as long as possible.

July 10, 2014 4:12 am

A quote from within ST’s quote:
” Emphasis would be placed on ensuring optimal fire allocation, which requires good operational mobility.”

A key point, and whether it is a 155 (G6), a 105 (Leo modified for Stryker) or 120 (AMOS/ NEMO) is secondary
– which ever fits in best with your logistics
– would guess that the “per mass” by SO in this quote takes the logistics (incl. speed of handling onto the SPG/ into the fire position) point of view?
““For casualties and damage 155mm is probably three or more times as effective as 105mm.”

Per shot maybe, and possibly even per MRSI (at certain ranges) but not in “per mass” or “per minute”.”

Funny that Kent of all contributors would classify D30 as crap? Outranged the 105mm’s that could be helo-lifted into position on hill tops in Vietnam – often times the 155 mm SPGs could not get into the game at all!
– still used today as coastal artillery for its excellent combination of range and punch

July 10, 2014 4:36 am

I don’t think Ken is the same as Kent. Kent was Armour, Ken is Arty.

I don’t see the lack of a specific logistics vehicle for the AS90 as particularly worrying, you got lots of stuff that you can chuck rounds in the back of that can keep up with it. In fact, x was suggesting using some of the old 432s as loggy vehicles in the FRES thread. Fill the back with 155mm and let it run with/to the SPGs. Hardly an insurmountable problem. If you’re desperate, rob the RM of some Vikings and use them as temporary cargo haulers. Extreme “all cost” case? Airdrop the ammo.

Red Trousers
Red Trousers
July 10, 2014 8:18 am

B Smitty,

Mortars are the emergency weapon always under a CO’s control, not subject to brigading of indirect fire assets as artillery is, quick into action.

Putting mortar bombs onto aircraft seems a backward step. You’d be subject to innumerable vagaries, and the general uselessness of anything the Kevins do. I appreciate that your comment does not make the case for removing mortars from the infantry, but I struggle to see why putting mortar bombs onto planes is an improvement over anything we’ve already got. Kevins can already drop bombs, even quite “smart” ones (although systemically they are still pretty dumb, given the stick monkey in the driving seat, and the convulsed chain of control over the radio to get him to a ballistic cone above the target).

Slightly Agricultural
Slightly Agricultural
July 10, 2014 9:15 am

@The Other Chris
I too wondered about 127mm, but nobody seems to make land systems in that calibre. I don’t know if that’s historical or for technical reasons.

Sabots might let you throw a 105mm shell further from a 155mm gun, but it’s not going to do as much damage as 155 when it gets there. Not sure the commonality savings would be worthwhile- either the 105 crews are binning the sabots before loading, in which case you’ve affected their logistics tail (as rounds now take up more space) or the saboted ammo is supplied seperately. In which case why not just use full-fat 155mm anyway?

July 10, 2014 9:53 am

@RT, some people are keen, armada.ch gives a summary (which misses a really light-weight one from Nammo Talley):
“Consideration has also been given to air-dropped guided mortar rounds, although such weapons have a smaller guidance footprint than winged missiles. This may force the drone to make a more precise ‘canned’ attack, flying directly toward the target, with munition release at a precomputed point, according to height-difference.

Several guided mortar bombs have already been developed. In 2011 the Alliant Techsystems’ Mortar Guidance Kit (MGK) for the 120 mm mortar entered service in Afghanistan. It employs GPS (which the US Army considers more suitable than laser homing in mountainous terrain) to give a CEP of less than ten metres. However, a 120 mm mortar bomb weighs around 15 kg, which is too heavy for multiple use on the RQ-7.

An 81 mm mortar bomb weighs only 4.1 kg, and General Dynamics has developed in partnership with BAE Systems the GPS-guided Roll-Controlled Guided Mortar (RCGM) for ground use. Derived from this, GD’s Air Dropped Mortar (ADM) has been tested under the US Army Research Development and Engineering Command (RDECOM) Precision Air-Dropped Guided Munition (PADGM) programme. It was first released from a C-123 and later from an L-3 TigerShark drone.”

July 10, 2014 10:30 am

Glad that many of you found the above interesting, and a good choice pics by TD.

Picking up on a few points, obviously I considered naval 127mm, the problem is that in technical terms it is a ‘gun’ not a ‘howitzer’, without getting too theological the key point is that it fires a fixed round, without a choice of charges, this choice is important because it minimises barrel wear and ensures that hills between battery and target can be avoided. Basically single charge guns for land service went out of fashion by mid-WW2. And as I intimated brass cart cases are logistic dead-weight in the age of breach obturation and primer magazines. Finally a land based fixed round 127mm would be impossible to use on any field firing range in UK for safety reasons (not forgetting that arty ranges in UK tend to be rather hilly)! The same points apply to tank ammo (less UK 120mm) and heavy AA. One of the 127mm naval shells I found data on seemed to have a notably poor percentage of HE fill.

Turning to air, the problem is command, or lack thereof from the army perspective. Air support is never guaranteed to the army, arty support is. Wise fire planners always plan an arty alternative to air support. The Brit Army was reminded of this, albeit with naval guns, in the Falklands!

Mortars have their place, but they are more range limited than guns. Furthermore the point of arty C&C arrangements is to be able to deliver the product of many fire units into an area, if you are trying to breakthrough a competent defence, even at battalion level you almost certainly need to suppress several target areas, some simultaneously. The problem with precision munitions is that you need precision targeting and identifying all the individual targets, even with UAVs this can be a big ask. Suppressing the area(s) is a lot simpler.

Finally, yes a new calibre would be a problem with the need to build ammo stocks. However, UK got around this when 105mm Abbot was introduced by using the old M1 shell and new reduced cartridge. One of the attractions of 122mm is that you might be able to do something similar (safety standards could be an issue).

The problem is a carriage design that is fast in and out of action and enables rapid traversing of a wide arc of fire, ideally 360 degs, all within an acceptable weight (ie girls and boys heaving it easily without being muscle marys, and you don’t need ginormous truck to pull it (meeting UK Road Traffic Act towing requirements).

New ammo design is not a notably big deal in the age of computers, BAe have just qualified a new 105mm (L53) shell filled with ROWANEX PBX (all it took was 3000 rds), and are developing a similar 155mm and a new carrier shell (RP smk seems to be the first cargo) and a similar HE 4.5.

July 10, 2014 12:42 pm

Minor correction: I think the “course correcting” fuzes are rather “trajectory correcting”. That’s the term I remember from since about 2000.

By the way; I have been collecting points (and motivation) for new articles on artillery myself (a series on MRL and one piece about future field artillery).

My older articles pointed out the cluster munitions ban and that smaller HE is more efficient in regard to “area perforated / weight of ammunition”. This was the point for DPICM,after all – and now it benefits the smaller calibre HE instead of the larger calibre cargo shells. The HE anti-armour and superior range arguments seem to keep 155 mm L/52 on the top so far, though.

What’s missing in Obsvr’s article is in my opinion
(1) The changes in the equations brought by the cluster munitions ban
(2) C-RAM considerations
(3) Some changes in what’s possible with artillery, driven by technology (don’t want to give details yet)
(4) Possible high/low combination, with the low end requiring deliberations about the future of heavy mortars

July 10, 2014 1:25 pm

@RT & ,

I wasn’t suggesting getting rid of either mortars, the 105mm or the 155mm guns. Keep them all. But rather than invent a new gun system, SUPPLEMENT the existing systems with new, air-dropped munitions.

I suggested an air-dropped 120mm mortar round because it is in wide service and production, has existing PGM programs underway, is more lethal than a 105mm shell, and is small enough to be “dense-packed”, compared to existing air-dropped munitions. A Reaper UAV could carry 30 on the two inboard pylons and still have room for Hellfires or a couple 500lb JDAMs. In theory, a Typhoon or F-35B could carry as many as 90 on six pylons. And these aircraft could theoretically deliver their entire payload in one pass, if necessary.

Two Typhoons could carry as many as three M1129 Stryker mortar carrier’s-worth of 120mm rounds.

July 10, 2014 1:40 pm

Smithy, I keep getting the image of F-4s volley firing Zuni rockets in Vietnam when you say that :)

July 10, 2014 1:46 pm


Similar! But instead of randomly distributing 10lb warheads all over creation, each round would be guided into a nice, pre-determined, range-independent pattern thanks to GPS/INS.

July 10, 2014 1:50 pm


Sorry forgot to say good post.

IMHO we should always consider need and requirement first then look to see what fits, when doing any defence stuff. THE NIH factor in my book is worthless. Eschewing the dead hand of Nato standardisation on new answers to old problems probably means a it all a non starter. But that does not mean it’s not, original, worthwhile thinking.

In that spirit I would like to ask pone question (from the point of a technical ignoramus:- (stop me if this gets too technical): –

Given the really expensive bit of the round, is the bit that goes bang, and the most expensive bit of the bit that goes bang, is the bit that makes the bit that goes bang, go bang. And the 2nd most expensive bit of all that is integrating it into shell….

Is there any difference in the shell design from a fixed to a non fixed case shell? In other words could we develop a casesless, or bagged, or separate shell case loading and fire 127 mm shells the same as the naval gun? Thus retaining commonality for the expensive bit? I thought he latest longer barrelled naval 5 inch was split loading?? (can’t find the citation for that just sure I read it somwhere… so could)

And so far out of left field how about this:- what about the Russian 125mm smooth bore- (SPRUT) I think they call it, or a nato version if you like.

Given it’s fin stabilised GPS and other guided rounds should be easier to design and that (we are told) is the future of artillery).

July 11, 2014 10:23 am

A couple of points on ammunition logistics. It’s useful to remember that there were two DROPS vehicles, the ‘Improved Medium Mobility’ and ‘Medium Mobility’. The former was the Foden and mostly assigned to batteries. The latter were RCT/RLC and delivered flatracks to the unit ammo points where they were picked up by the battery IMMLCs.

BAe came up with an armoured ammo carrier design in the early 1980s and made an unsolicited offer to MoD, it wasn’t accepted. Armoured ammo carriers have pros and cons (ignoring costs), the pros are obvious – mobility the same as SP guns and protection for ammo if the battery comes under CB fire. Of course the introduction of autonomous guns (ie self-surveying and self-orienting) has opened up new tactics for high threat environments and AACs are less required than perhaps they once were.

The cons are more complicated, but basically it’s the manpower implications of double handling ammo and ensuring sufficient ammo is on hand. It’s also useful to note that unlike the US all UK arty ammo comes with fuzes fitted, US 155 ammo still comes plugged (just like WW1!) and fuzes have to be fitted in the battery, which takes time and effort. This doesn’t matter too much given the M109’s low rate of fire (and not forgetting the US arty isn’t noted for its speed of response to calls for fire!).

AACs have to go to the place where the ammo is (presumably the exchange point with RLC), unpack it, load each shell and propelling charge into the AAC, this takes people and time, then return to a gun where ammo is then transferred to the gun. What happens if there’s a run on a particular types of ammo when the AAC is away? AS90 carries 48 rds but of various types and its rate of fire means one type could run out while the AAC is away. The obvious solution is more than one AAC per gun, and a further increased manpower bill. With DROPS one or more flatracks of 170 155 rounds (in 10 ULCs) can be dropped behind each gun and easily picked up if the battery moves, The ULCs may only need opening one at a time (depending on the mix of ammo types) and rounds transferred to the gun a few metres away, the first time individual rounds are handled since the ULC was filled years before. The battery has rough terrain fork lift trucks so if ULCs need to be distributed (eg ammo types held in relatively small quantities) or empty ULCs replaced by full ones, it is easy to do. An AAC capable of handling ULCs might be a solution to the manpower issue but the ULCs still have to be handled off the flatracks into the AACs, but a ULC weighs around 1300kg so some fairly complex arrangements are needed in an AAC to lift and stow them and the onboard load would probably be a lot less than with individual rounds.

The short answer is I’m not sure, it hasn’t been an arty matter since 3.7 HAA left service in the 1950s! From what little I’ve seen of fixed rounds (never did get to fire any from my Centurion OP tank) have short ‘threads’ on the top of the cart case that presumably engage with something on the shell below the driving band.

I can’t see any reason why the same shells could not be used in a fixed round or with separate loading bagged charges, or even a separate loading cart case. Obviously in each case the chamber would be different and hence the ballistic performance would be different. Even if a different shell was required the differences would probably be external and very slight and all filled on the same production line. My doubts about 5 inch are that it might tip the carriage weight to too heavy, hence my preference for 122mm.

HE shells are relatively cheap, it’s things like Illuminating that are expensive. Hopefully BAe’s new HE filling techniques with PBX will reduce the costs by simplifying the QA methods.

Projectiles in flight have to be stabilised, this is either spin or fin. To date the relative cost, complexity and non-lethal weight/space of fins have not made them attractive for arty.

@ SO

the problem with cluster munitions was the large number of blinds, the claimed 7% was a sick joke. (the problem was not just arty, the air delivered ones were just as bad, and going carefully past vegetation with these UXBs dangling all over the place is something best avoided. I don’t think it changes much at all, AFVs are best dealt with by newer smarter munitions, and airburst is now available with all HE.

Active C-RAM may be useful in insurgencies, otherwise it’s just a high priority target. CB radars are a problem but they have to be supported by the rest of an effective CB system. They too are high priority targets and the CB problem can be made more difficult with the right arty tactics, eg battery manoeuvre areas.

John Hartley
John Hartley
July 11, 2014 11:39 am

Rambling on. I suppose the cheapest option is just to buy a few 155mm lightweight M777. My leanings are to bring back the 175mm both for the Army & a new Naval deck gun version. Probably be judged too big, so what about the RN 5.25″ high angle, dual anti aircraft & anti ship gun of WW2? Think that’s a 134mm? I would not want that to be a UK only project, but if others joined in (France, Germany, Italy?), we might get a common calibre for tank, medium artillery & a Naval deck gun. The HE & guided shells could be common, even if the propellant cases varied with each application.

July 11, 2014 4:35 pm

I was saying that the D30 was in my opinion a piece of crap. I saw them in Afghanistan and in Iraq and they were crap. I was a little tike in the Vietnam era, so I did not see them in action there. Like I said, the ones that I saw in Iraq and Stan were crap, so I will give the benefit of the doubt that if the gun were maintained well and new with a good trained crew, maybe it would be a good gun, but not what I saw. Honestly I would have taken a M114 155mm over it. I was not a bit fan of our M198 155mm piece. I was deployed originally with a M101A1 105mm howitzer in my first Marine Corps Artillery Unit. I loved that gun. I love the M777 and have had a chance to see the M119 105mm or as you guys call it the L118 and love it, but if it could have the 155mm punch. I have seen the AS 90 in action and was impressed with it. Just like the M109, it is an older weapon system. Now the Russian 2A65 Msta-B is a very good artillery piece for a 152mm towed piece. They use is on their self propelled types also. 28.9 km range is also good.
RedLegs for ever! Your cousin from across the pond. USMC Artillery.

July 11, 2014 5:02 pm


when you find a good thing, you want more of it?

July 12, 2014 3:38 am

@ JH M107 (175mm) had a good carriage, shared with 203mm, but limited traverse. However, the gun was not so good. Only three charges (could be fixed) but notably large dispersion.

@ ken

I agree on D30, I did a technical evaluation on one as a course project many years ago. It is robust as anything and very simple maintenance (hence its third world popularity, but it trades too much off for its direct fire capabilities, this of course was Soviet military thinking. As a Soviet regimental gun it was fine because there were umpteen divisional and army battalions as well.

You should note that M119 (or L119 as it was known in UK service) is not the same as L118. L119 fires the old 1935 ammo with a somewhat poor range although the newer US cart improves it significantly. L118 has a totally different ordnance (barrel assembly in your terms) firing completely different ammo and unable to fire the M1 type (the electric primer is a bit of a gotcha). BAe claim that the newer HE shells are as effective as 155mm M107, although this will only be against some target types. L118 also has substantially greater max range than a 155mm M114.

AS90 is only 20 years old (same age as PzH2000), what distinguishes it from M109 is the degree of turret automation, the capability to deliver 3 rounds in 10 secs, and 6 per minute (actually more in practice) and 48 rds onboard. It also has an aux gene so no need to keep running the main engine for most of the time.

July 12, 2014 2:37 pm

Ammunition HE filler weight (approx):

155mm, howitzer, M107=6.9kg
155mm, howitzer, M795=10.8kg
120mm, mortar=2.9kg
127mm, naval=3.5kg
122mm, howitzer=3.5kg
105mm, howitzer=2kg

July 16, 2014 2:23 pm

I love the twin barrel sp….. double the firepower and delivery. Think in a 12 gun battery, you would effectively be two batteries in one. Wow!

Thanks for the info on the L118 and L119, only got a chance to see them in action in Iraq and in Afghanistan. One with our 101st Air Assault Div and the other with the Royal Marines. Looked like an awesome gun. The D30 was designed to be a fill gap gun, one that the crew did not need to be well trained on and simply line the batteries up hub to hub and fire away. Simple and useful for their tactical purposes. Overwhelm by intense and massive fire in an area. Personally, I like shoot and scoot or even divided battery, say in sections of either 6 guns or 3 gun sections. You can achieve much with a split battery. We used it a lot in the Marine Corps for counter battery fire and targeting.

Your cousin from across the pond,

July 16, 2014 2:27 pm

That wasn’t me mate. :)

Swimming Trunks
Swimming Trunks
August 15, 2014 12:21 pm

What about this Russian towed Gun/Mortar? It appears to be designed with airborne/heliborne operations in mind…



[…] the 105mm ammo then the ration of ammo carried increases in favour of the 105mm. This is quite an interesting post over at Think Defence. The big question for me is whether of not the M777A2 could be lifted by our […]

Alan Erskine
Alan Erskine
March 22, 2015 4:00 am

The following is my first post on this forum.

I doubt the validity of the ‘howitzer’ or the ‘light field gun’ concept in modern warfare; they are heavy, require a large crew and expensive. A 120mm mortar is a much less massive system, requires fewer crew and is much less expensive to purchase and maintain and the ammunition is more powerful than any 105 round available. Range is somewhat less than the 105 with ‘normal’ ammunition, but potential advantages include the ability to operate (already available) guided rounds as well as top-attack, which provides easier penetration of buildings, which must be considered in this day and age.

If range is an issue, then a RAP (Rocket Assisted Projectile) can be used.

The already-mentioned NEMO is a fantastic system. It is lightweight and can be mounted on a number of platforms, requires a small crew and can fire ‘shoot-and-scoot’ more effectively than any towed system. It also has a much higher rate of fire than a towed system. As well, an armoured vehicle affords more protection to the crew than a towed system can provide.

In addition, NEMO can be mounted on small water craft; a 105 cannot. This latter option provides considerable firepower for amphibious operations and riverine warfare.

Let’s not forget the possibility of a simple, self-propelled system such as the Polaris Ranger Fire Support System or similar. Light, four-crew members, fast and a ‘shoot-and-scoot’ capability a towed crew can only dream of (and hope for).

Also, there is potential for considerable growth in variety of ammunition for a 120mm mortar. Submunition rounds asside, guided 120 rounds are already available (STRIX etc) and the possibility of UAVs being launched (already prototyped for the 40mm under-rifle grenade launcher) is to be considered; if it can be done for a 40mm, imagine the possibilities for a 120mm system.

March 22, 2015 6:55 am

Conventional artillery is dead this is the future