My object here is NOT to exasperate those CW types who venerate the 25 pdr (although I admit to some trollishness in the header ), but to see if an alternative approach would have been better as a whole.

DISCLAIMER: I began to consider this for the '25 pdr in tanks' thread, but decided to start a new thread. Now PLEASE, can we avoid the standard 'Sargent is an Anglophobe' and 'the 25 pdr is the best gun in the world' posts? I KNOW the 25 pdr was/is a great gun. What I am looking for is whether its adoption was benefical to the British war effort as a whole.

25 pdr problems:
1) It introduced a new caliber just when a major war was coming. Now this isn't hindsight, they knew a war was coming, that's the only reason they got the 25 pdr. The 25 pdr required new tooling for tubes, carriages, and ammunition = major production problem.
2) It effectively took the 18 pdr out of service, first by having the most modern MkIV 18 pdrs converted to 25 pdr MkI, and then by taking 18 pdr ammo out of the development and production chain.
3) The improvement wasn't worth it.
4) IMHO a new field gun was not the most important need - explain this in a few minutes.

Alternatives:
1) Keep the 18 pdr. Large stocks of guns and ammo existed and presumably machinery in 18 pdr caliber existed; and
2) Develop improved shells for 18 pdr. The actual HE carried was not that different (there were so many 18 pdr shell types that exact comparisons are difficult). The R&D effort that went into 25 pdr shells could have made improved 18 pdr ammunition.
3) Better carriages for the 18 pdr; I am not so much arguing that the existing guns be retained, but that the caliber be retained for production and inventory reasons. The tubes were the important part; new carriages were pretty easy in comparison but new barrel-making plants and rifling machines present production difficulties. The old guns could be initial and emergency equipment and improved 18 pdrs become the standard field gun. New propellant charges and higher elevation could have made the 18 pdr capable of matching the 25 pdr's increases in range over the WW1 18 pdrs.
4) Develop a whole new caliber. The Brits had made a prototype 105mm howitzer Between The Wars. I don't particularly like this, you have the same production problems as with 25 pdr. The only real advantage would be caliber compatability with the French (and later the US, but that's hindsight).
5) Improve the 4.5" howitzer. Now this was a great little gun, but it had poor range. However a new gun in the same caliber could have come out performing like the Soviet M1938 122mm (if I was doing the 'go back in time' bit, I'd take M1938 blueprints along ).
6) IMHO the HE delivery advantages of a new 4.5" howitzer would more than cancel out the advantages gained from going from 18 pdr to 25 pdr.
7) This would mean having two calibers instead of one in the FA regiments, but the Brits had managed to get through WW1 with two calibers and everybody else managed WW2 with two calibers (or more).

Summation:
The 25 pdr adoption created problems in supply of ordnance and ammo in the early war years. Improving the 18 pdr while still making sure it could use up all that nice available old ammo would get improved performance with fewer production and supply problems. A new 4.5" Howitzer presents the same advantages of existing production machinery and ammo stocks, but offers improved HE delivery over the 25 pdr.

The British needed improved artillery, but it is my contention that they could have gotten it quicker and easier without introducing a new major caliber that was incompatable with anything else in service.

I have to admit that the British almost perversely adopted a range of new calibres in the 1930s, for the navy as well as the army (4.5 inch and 5.25 inch). The army not only got the 25 pdr but the 5.5 inch as well, and the AA gun became a 3.7 inch. I agree that this was largely unnecessary and must have caused production problems (especially since the navy continued with new 4.7 inch as well as 4.5 inch - nuts, to coin a phrase). They seemed to have become obsessed with attaining some sort of theoretical ballistic perfection for each type of gun.

Nonethless, the 25 pdr does seem to have been one of the all-time great guns, so it would be a shame to lose it...

Tony Williams: Military gun and ammunition website and discussion
forum

Uh, Sarge? The exact same argument could be made against the US replacing the 75mm M1917A4 with the 105mm M2.

Or against the Germans replacing the 7.7cm FK 16 with the 10.5cm le.FH 40.

And so on and so on?

Conditions were a tad different. The US had time to get the 105mm into service (even if the gun to see action before TORCH was the 75mm), but we still ended up short of 105mm ammo in 1944 (thanks again, Congress). Besides the original US plan was to mix 75mms with the 105s.

The Germans did not have a huge inventory of guns and ammo in service to take into account. They could start with a clean slate, and the 105mm was not a new caliber anyway - ie, they had machinery for it.

You will note that I did not argue against new guns, I argued against a whole new caliber for which there were no shell stocks and no production facilities. IOW a performance-improved 18 pdr made on existing 18 pdr boring machinery and firing existing 18 pdr shells while improved shells were being produced gets new weapons into service quicker - and they knew they had a war coming.

I stipulated its greatness. But how great would it be considered if the British had lost the war because of an ill-considered caliber change that disrupted the production and supply chains?

I like the 25 pdr. I'm just looking for better options. Wouldn't a 25 pdr MkII carriage with an improved 18pdr tube be just as cool?

Range considerations aside, was there a significant difference in the effectiveness of the 25pdr HE round vs the 18pdr HE round?

Methinks the essence of the 25 pdr was its flexibility. It could be rotated 360 degrees in no time at all, and could fire up to 17 rounds per minute (the existing record, in combat). Ammunition was light enough to be manhandled with relative ease. The standard in crash-action drills was to have a battery in action in 3 minutes.

No, in the sense of firepower, it wasn't the best gun... but a well-trained field regiment working with the Commonwealth fire control system could devastate any designated target within minutes. I can't see how the 18 pdr could have improved upon that.

I can't find specific data on 18 pdr performance, it would largely depend on the quality of shell - and there multitudes of different 18 pdr shell. IE, if the same quality steel is used the 25 pdr is going to be more effective, but if good steel is used in 18 pdr shells vs the crap steel used historically in 25 pdr shells, the HE charges should be about equal.

The 18 pdr is considered approximately equal in effectiveness to French and US 75mms (since they were they same), but WW2 US 75mm shell carried at least as much HE as the 25 pdr despite the overall shell weight being 40% less. So if the historical British 25 pdr shell is used, I can't see any great difference from 18 pdr.

But would I welcome any hard data on shell efectiveness.

There was absolutely nothing preventing the British from putting a performance-improved 18 pdr tube in the 25 pdr MkII carriage. The performance you cite was dependent on the efficiency of the carriage, not the gun tube.

IF the shell effectiveness does not overwhelmingly favor the 25 pdr, it would have made more sense from the production and supply standpoints to stick with the 18 pdr caliber in the new gun.

I think Tony Williams was right, the Brits at the time pursued a whole lot of new calibers apparently just for arcane ballistic reasons instead of practicality.

The 25 pdr HE shell contained 18 oz (510g) of HE, the WW1-era 18 pdr HE 13 oz (368g).

Tony Williams: Military gun and ammunition website and discussion
forum

The Germans did have quite an inventory of 7.7cm guns, yet they made the deicision in 1930 to convert them all to 7.5cm with 7.7cm being deleted as a standard caliber.

As noted, the Brits decided on a 25-pdr (94mm) gun how to replace the 18pdr (84mm) gun and the 4.5in (114mm) howitzer. While the Brits designed a very nice and competent gun, the weakness was lack of shellpower caused by the poor steel in the projectile and the relatively small bursting charge.

The US probably came out ahead in concentrating on the 105mm howitzer from the start. The 75mm gun held on as long as it did because of the horse drawn artillery requirments. Once the decision was made to fully motorize, the 105mm was the best solution.

<Mr. Picky> IIRC, the 25 pdr is 87.6mm caliber. 94mm would be 3.7", which in the case of the 3.7 Howitzer also used a 25 pound shell. </Mr. Picky>

Sarge, you're a bloody anglophobic-yankocentric etcetcetc



Jokes asside, this is a good point.

On the production side, the 25pr was, as we all know, limited by the need to be retrofitted into the existing 18pr gun stocks. 87.6mm being the biggest they could hog out the 18pr's lose liner out before they ran into structural problems.

Given this, it seems as if there might not have been too much difference in the gun making machinery required by the two weapons. If they both use the 'same' (the 25pr was 1.5" longer, probably minor other differences?) liner, the rest of the barrels have to be at least roughly simmilar. And in the same vien, I'm pretty sure Australian production of the 25-pr used the 18pr plant and machinery we'd bought surplus (almost new) at the end of WWI.

So the production angle might not have been that much of an issue, in any event, any new production facilities would suit the gun being made.

On the shells, 5oz difference is only two Mills Bombs worth, so I've got no trouble seeing the 25pr as a minor improvement at best, but the steel grade is the big point IMHO. The 25, like the 5.5" was designed to use crap steel to keep the costs of production down. So any improvements to the 18 that would need better steel, have to viewed as haveing a negitive effect on the war effort in comparision to the same number of 25pr shells.

How this would pan out, I can't even guess, but either way we wre talking about a sh1t load of steel.

<Mr. Super Picky>
Ordnance QF 3.7" Mountain Howitzer Mk.1 on Carriage Mountain Howitzer Mk.1

Ordnance
Weight: 3cwt 3 qr (191kg)
Length: 46.8" (1,189mm)
Caliber: 3.7" (94mm)
Breech: Interupted Screw, single motion
Fireing Mech: Percussion
Maximum Range: 6,000yrd (5,490m)
MV: 973fps (297m/s)

Ammunition
Type: Semi-fixed
Nature: HE
Fuses: Percussion, TIme
Weight: 19.5lb
Charges: 3

Carriage
Type: Two wheel, split trail
Recoil: Hydro-pneumatic, vairable
Top Traverse: 20d (356mil) left and right
Elevation: 40d (711mil)
Depression: -5d (89mil)

RoF: 12rpm
Detachment: 9
Weight in Action: 14cwt 2qr (730kg)
</Mr. Super Picky>

The 3.7" AA gun fireing a 28lb HE shell, just for compleatness.

I do like the idea of the PIP 4.5", there's nothing stopping it from useing the same platform traverse as the 25pr, and if the barrel was increased to get the range, a 35lb shell is still going to do some dammage in direct fire.

My only problem with the concept, is ammo cost, it was obviously a sensitive point to British authorities at the time. A 4.5" is going to be useing a round 50% larger than the 25pr, I don't expect the costs would have scaled in the same term's, but I'd say there's little question the 4.5" would have been more expensive to feed. The question being of course would it have made any difference? The logistics alone of shipping 3 for 2 would make a big difference unless the RAA and by extension the whole Army shifted it's artillery dictrine.

The 4.5" would be more effective per round, but we then we come back to the Supression Vs Destruction argument, and for better or worse the CW was hooked on supression and the 4.5" diet wouldn't have fitted in too well with that.

How about bigger stuff, could the 60pr have been PIP'ed, was the 5.5" for its sins the better option (the less said about the 4.5" GUN the better), or should the 6" 26cwt Howitzer have been streched out another 5-10,000 yards?


shane

I think the reason why the 25 Pdr was adopted was to indeed gain better ballistics, rather than better end effects (or the shell exploding). However, it was adopted because of what were percieved to be obvious deficiencies in the previous field guns, the 13 and 18 pdr which had been found in WWI to be inadequate to the task (too short a range, too smaller bursting charge).

Points which are in favour of the 25 Pdr, over heavier calibres are the range and the rate of fire. Points against it are the relative lack of effect and the relative complexity of the gun carriage. The first two were often remarked upon by its victims, the last two were noted by its users.

The possibility of adopting the 4.5in calibre is an interesting one but it comes back to whether or not the cost was justified or that the machinery of manufacture could make the larger tubes as easily. As has been noted, the existing gun lathes, could, with adaption, make the 25 Pdr tubes. I suspect they wouldn't have been able to handle the larger 4.5in tubes, as easily.

Regarding putting 18 pounder tubes on 25 pounder carriages, I thought the Brits did just that early in the war when there was a shortage of 25 pounder tubes and surplus carriages.

The 4.5" Howitzer Mark I served through both World Wars. The tooling for both tubes and ammo already existed. Possibly not as much tooling as for 18/25 pdr, but the CW forces went through WW1 with about 1/3 of the Field Artillery being the 4.5", so there must have been some...

As you noted about the 25 pdr, one goal was more range. The 4.5" Howitzer's big drawback was a range of only 7000 yards.


One interesting idea that just came to mind - if there was any 18 pdr shrapnel left over from the Great Blood in the Mud, that might have been real handy for encouraging AT gunners to not make a nuisance of themselves. A little smoke in front of the tanks, some shrapnel on the AT positions (after you figure out where they are) and Bob's yer uncle... There was no shrapnel for the 25 pdr.

Shrapnel got a bad name in WW1 for not coming equipped with little tiny wire-cutters and not being able to destroy trenches. But I can see where it could be very useful against soft-skin and open-top vehicles. And troops in the open which of course is what it was designed for.

Other way around. The 25 pdr MkI was the 18 pdr MkIV with a new 25 pdr barrel. Colloquially known as the "18/25 pdr."

Oh, there were some but were there enough? Would be worth trading the 5.5in say for the 4.5in? I suspect not.




The major reason why shrapnel fell into disuse was because of the fuses. They were too unreliable. It was one of the major reasons why it failed in its wire cutting duties, rather than necessarily because the shrapnel was unable to cut the wire. Get too many blinds they become a hinderance to your own troops, as well as the enemy.

We are speaking here of the 4.5" Howitzer, which was Light Field Artillery. The 4.5" Gun was a 4.5" tube in the 5.5" carriage, which was Medium Artillery. The 4.5" Medium Gun had a shell like the 25 pdr, crap steel and very little HE. Aside from a slightly longer range than the 5.5" Medium Gun, it had nothing to recommend it.

As I said, about 30% of the Field Regiments in WW1 were 4.5", so there were some around.

Anyway, it was a neat gun (so neat it never got past Mark 1, the original was good enough throughout its service life). With a little (okay, a lot) more range it could have been more useful in WW2. As I said, if I was doing it my goal would be something like the Soviet M1938 122mm Howitzer, only in 4.5" because the boring equipment and shells were available.

Or if you retain the 4.7 inch calibre for the navy instead of going for the 4.5 inch you might decide to simplify production and design a 4.7 inch gun/howitzer to fire the new 62 lb shell developed for the L/50 destroyer gun...

Tony Williams: Military gun and ammunition website and discussion
forum

Really? We're talking about the 4.5in Howitzer? Really?

Please KingSargent, give me some credit. I am well aware of the difference between the two weapons. My point was that the lathes which were capable of manufacturing larger calibre gun tubes were more than likely already busy making 5.5+in guns for the army or 4.7+in tubes for the navy. About the only space capacity would have been the 4.5in guns manufactured for the army.



If you are willing to accept the caveats of lower ROF and increased weight of carriage.

Ah, I see now. You confused me with the reference to the 5.5" gun. I must confess I wondered what was going on, I was pretty sure you knew the difference.

AFAIK, the lathes are only critical for the length of tube. That's why the US 57mm was longer than the parent 6pdr, we had more lathes long enough to make them 50 cal while the British had to use 43 calibers on MkIIIs.

What would really matter would be the boring machinery, and there shouldn't be a problem with making shorter 4.5" tubes on short lathes. "Build 'em by the mile and saw them off as needed..."

Huh, me, what? I didn't do it. I didn't take no guns. Don't bother to look in the trunk, nuthin' there, occifer.

-Mark 1

Ahhhh... The Bay Area Reflex in action!

I have taken a quick scan through this topic, and I may have missed this point if someone else raised it....

The 25pdr was created to replace both the 4.5in howitzer and the 18pdr gun. The 18pdr could not do what the 4.5in howitzer could, in terms dropping HE shells over intervening landscape. The 18pdr was a gun, pure and simple, firing fixed ammunition, so that it could not be varied according to targets and conditions. Also, as it was always firing with a relatively hot charge, barrel wear was a factor.

The US did not appear to have a WW1 howitzer, having taken the French route and adopted the 75mm gun, which was fine when firing against troops in the open, but was not effective against trenches and the like, hence the Westervelt Board recommending a larger calibre weapon with similar performance to the 25pdr, to the extent that the 105mm was actually a gun howitzer.

Last point about the 18pdr - it was designed as a wire wound gun, using an obsolete manufacturing process, even thought later models were built in different ways. The 25pdr was a more modern auto-frettage weapon.

The other way around, 25pdr guns were built using 18pdr carriages.

It was the 17pdr that first went into action on the carriage of the 25pdr.

Actually, there were at least two, although the main one was the French or French copy 155mm. The other design never saw service AFAIK, being overtaken by events. This was a 3.8" howitzer.
You are correct that the US did not have a light field howitzer in service during WW1, unless the divisions that served with the British had some 4.5" 'loaners.'

Wire-wound or auto-frettage, there still needed to be a machined and bored liner for the shell to go through and to hang the reinforcing material on.

The Westervelt Caliber Board of 1919 laid out an artillery design program that guided the US Army for decades. One of the keys findings, was that for each of the classes of artillery, there should be both a gun and a howitzer.


Light Artillery: 3in gun/105mm howitzer
Medium Artillery: 4.7-5.0in gun/155mm howitzer
Heavy Artillery: 155mm gun/8in howitzer
Super-Heavy Artillery: 194mm-8in gun/9.5in howitzer

Railroad Artillery: 8-10in gun/14in gun/12in howitzer/16in howitzer
AA guns: 3in gun/4.7-5.0in gun
Pack Artillery: 3in gun
Infantry Accompanying Gun: 2.5in gun
Trench Artillery: 6in mortar

The board also called for immediate motorization of all artillery except light artillery and use of all-wheel drive trucks for ammunition supply.

You look back from 26 years later (end of WWII) and realize just how much of this plan came to fruition.

Exceptions: 3in guns for pack and light artillery became 75mm because designs were based on existing stocks of French 75mm. 4.7-5.0in gun became 4.5in to standardize with Brits. 9.5in howitzer became 240mm to base on existing stock of 240mm. Railroad artillery never went past 8in guns. Small AA gun upgraded to 90mm. 105mm AA gun also developed. No infantry gun or 6in mortar.

Would not the "effectiveness" of the gun be a function of its role (the "Suppression" vs "Destruction" argument); ammunition types and performance including its shell weight/filler weight (explosive effects as well as shrapnel), fuse, etc; its adaptability to various roles, high angle/low angle fire, traverse both coarse and fine (speed of traverse), sights, fire control, rate of fire, crew training and morale (for those "close in situations"), cost per round, the ability of the plants to manufacture both gun and ammunition, etc ?

It is one of those eternal questions like "How long is a piece of string?". There is no right or wrong answer.

(By the way - what of the US Army units that were equipped with 25 Pdr because of the shortage of 105mm ammunition?)

Frank

Tony, do you have a discussion thread/forum for "The Foresight War"? I just finished it...

The 105mm was a gun-howitzer? I Wasn't aware of that.

I am finding out that my trivia knowledge is totally inadequate on anything but small arms. Any good reference links? I read what is here, but my memory isn't as good as it was...

Yep, the 105mm was until recent upgrades considered a gun/Howizter. Our Canadian ones recieved an upgrade (105mm C3) with a longer barrel, muzzle brake, reduced shields, and beefed recoil and trails. I think they have a range of 18km with assisted ammo. Don't know if they still refer to them as gun/howitzer, become more of a gun now.

How well would the 18pdr do as an AT weapon? For awhile the 25pdr was the only real effective AT weapon they had in North Africa.

There have been some comments posted in the 'Tanknet Authors' thread at the top of the General Military forum, and I have a section of my discussion forum devoted to the book.

Tony Williams: Military gun and ammunition website and discussion
forum

Penetration of the 25 pdr AP shot was about the same as the 2 pdr AT gun. It did more damage when it penetrated, but the hit probability was lower due to the more curved trajectory.

Tony Williams: Military gun and ammunition website and discussion
forum

What about them?

IIRC, the 3" AA gun was put on 105mm howitzer cariages to make the 3" AT.
The French 75 was used in the Cannon Companies of Infantry Regiments, replaced by short, light 105mm w/o gun shields sometime before 1944. Unless the 2.5" was a replacement for the 1 pdr, in which case it became the 37mm AT gun.

The Westervelt Caliber Board seems to have missed the boat on AT guns, but otherwise, pretty good!

If you guys don't mind answering a dumb question from a non-Imperial, non-military person: how do those pound-'calibers' relate to the mm/inch gun bores i'm more familiar with? It's one of those questions i've had for years, but never really dared to ask (i can be shy, sometimes).

Thanks in advance.

Generally:
1pdr= 37mm;
2pdr=40mm;
4pdr=50mm
6pdr=57mm
9pdr=65-70mm
12 to 18 pdr=75mm or 3" range
22pdr=88mm
25pdr=87.6mm (WW2 fieldgun) or 4" (WW1 naval gun on DDs. Cruiser and BB 4" fired 31# shell)
60pdr=4.7"/120mm

Basically, designating a gun in "pounds" goes back to the days of roundshot, when a "12-pounder" fired an iron ball weighing 12 pounds. This was very simple and uniform since if you knew the specific gravity of cast iron and simple solid geometry you could come up with the bore diameter. Well, you could if it weren't for the fact that the windage varied from country to country (French guns of Napoleonic period tended to have less windage than British, for example). Even worse, weights varied from country to country (a French 8-pounder was about equal to a British 9-pounder), and howitzers were sometimes rated by the weight of the shells which they fired (naturally lighter than a solid iron ball of the same diameter) or even the weight of a stone ball that would fit the bore...

When rifling became common and enlongated ("cyclocylindrical" was the term used in the early days) projectiles became the rule, most countries went over to designating the bore diameter. But the British continued to use the old system, interspersed with the new, until after World War II. Speaking as a non-Imperial, I could never understand why three guns all coming into service about the same period would be known as 17-pounder, 5.5 inch, and 95mm ...

So the only real solution is to memorize data about British artillery. The designation in pounds gives a rough idea of the caliber, but there is no way to get an accurate bore diameter from it. As an example, the 18-pounder has a bore of about 3.3 inch diameter, while the 17-pounder and 12-pounder both are 3 inch (the 17-pounder is an anti-tank gun, so fires a solid steel shot weighing 17 pounds, while the 12-pounder fires a shell weighing 12 pounds more or less). Sorry that I can't be more helpful....

Hojutsuka

Ah, yes. That's much more helpful than my post. Thank you, Sargent. The only quibble I have is that 22pdr. I've never come across a "22pdr". I would suggest instead:

20pdr=83.8mm
32pdr=3.7in/95mm

Hojutsuka

22pdr was a Brit designation for the German 88mm naval gun (some sources say the WW1 version was 87mm).
4pdr was German 50mm gun used on older TBs.
9pdr was a French (and Austrian IIRC ) naval gun.

I should add that the 'pounder' designations are not necessarily accurate. For example, the 57mm calibre became associated with the 6 pdr designation in the 19th century. This relationship stuck, even when the projectile weights varied.
So the APCBC Mk 9T shot for the 6 pdr AT gun weighed 7 lbs.

You might find the article 'A Primer on Cartridges' on my website of interest.

Tony Williams: Military gun and ammunition website and discussion
forum

Thanks everyone. I already feared it wouldn't be something easy...

" I could never understand why three guns all coming into service about the same period would be known as 17-pounder, 5.5 inch, and 95mm ..."

This isn't that hard - in comparision

GUN's as in low trajectory weapons got the pound designation as noted and so well explained. But in British service 'shell' fireing wepaons back in the ML period, howitzers and mortars ended up be codified by bore diameter as the shell weight could vary alot.

So later on you could have say the 60pr BL gun and a 5.5" BL howitzer both with the same caliber.

By WWII I get the impression that they were returning to the traditional roots of the system just as it was dying. If a weapon was provided, or it was planned to provide it, with solid shot, then it was a pdr. If only shells were going to be used with it, then it got an inch.

I also think metric got used (apart from foreign weapons that were metric US for example) as a second system for when the inch or nearest nominal had already been used and a second weapon of the same caliber was introduced. eg 77mm rather than 76 (US gun) or 3", and 95mm rather than 3.7" (already two in service).

shane

PS Anyway it is easy! Just look at them as names and don't expect to get a detailed spec out of the shortened form commonally used. I don't see any reference to engine size of fuel milage in 'Ramcharger' or 'Camaro.' It's no worse in its own way than US M numbers, M1 this and M1 that.

Actually - for this debate I think this site is pertinent and actually gives a lot of data to be used to carry it forward....

British Artillery in World War 2 - Effects and Weight of Fire particularly Table 4 – 25-pdr Equivalence that shows that the 18 pdr was regarded as inferior in both weight of shell and its effect compared to the 25 pdr (80% and 70% respectively).

(the whole site is fascinating for the information on the Royal Regiment of Artillery, its organisation, tactics, weapons, etc - an damn fine site)

Frank

Perhaps it more along the line that guns were always given the weight of their principle round, howitzers by their calibre. The use of metric came into play to stardardise on a single measurement of weapon bore becasue the same weapon could fire different weight of round dependant on its mission.

The 25 pdr, 17 pdr, 6pdr, etc were designed at best in the first year or so of the war (and in the first and last cases were pre-war designs) so were before the decision to use metric (which seems to have occurred with the introduction of US equipment on a large scale at or about 1942). There is probably paperwork in the National Archives (formerly the PRO) explaining the chnage but needs someone to dig it out.....

Frank

Sounds plausible, but the timing doesn't match... The 30pdr project started in March 1943, and its final product, 'Ordnance QF 32pdr', was christened after June 1944. There is also the 20pdr that armed most Centurions before the advent of the 105mm L7. In short, even if the introduction of US equipment on a large scale at or about 1942 was the cause of a decision to go metric (and US itself wasn't entirely metric at the time anyway, as seen by the 3inch AA and AT guns and 8inch howitzer and gun), any British decision to go metric doesn't seem to have taken full effect until much later than 1942, very possibly not until after the end of World War II.

Hojutsuka

The best example of my theory (if it can be called that) is as Hot mentioned 3" guns. We had the:

3" 20cwt wich is the old school caliber and weight system harking back to when Hank 8 used to by guns by the pound, and note as AAA it's a shell firing High Angle weapon.

The 3" CS Howitzer

17pdr

76mm (US)

and 77mm in the Comet.

Looking at the last three, no inch names, all low angle guns, all firing proj's of about the same weight and all with the same bore diameter 3"/76mm.

shane

PS capt_starlight, Nigel the bloke responciable for that site you lined to, floats around here from time to time, also over on Tony W's board.

Shane, the main reason for retaing the different nomenclature for most of these was to facilitate ease of supply. So, for instance, the US 76mm and 3" were actually both 76.2mm guns, but they used different cartridge cases, so the projectiles were interchangeable, but the complete rounds were not. So if both were designated as 76.2mm guns you would have had to read the fine print of the supply order to make sure you ordered the correct one. And the same for the 17pdr, 77mm and 3" CS howitzer. All were 76.2mm, but they were very different rounds, the differing designations were made to help keep clear which was which.

And it got even more complicated, the rounds of the US AA Gun, 3", M1918, M1 and M3 differed from those of the US AA Gun, 3", M1917, M1925M1, M2 and M4 and were not interchangeable.

Rich I know

Easy of suppy is WHY they gave all those 3" distinctly different names, I was commenting more on how they came up with them.

shane