Pea Shooter of the M4

The British volunteered to supply the US with their 17 pounder AT gun for the Sherman, and the US turned them down. Why? They did not want a British gun on a US tank, later it was said that they turned down the 17 pounder offer because they were exploring the possibility of putting a 90mm gun on the Sherman, which is ludicrous, because the 90mm would not fit the turret of the M4. Why did the US drag it's feet to upgrade the M4 so that the crew would at least have a fighting chance against the German armour?

 

This is not exactly correct. The British and the Americans both recognized the need for a more powerful main gun in 1943, but the British didn't exactly "offer" to supply the 17 pounder. We Americans were working on a new turret designed around our own 76mm M1 gun and the special tank destroyer vehicles which would house the 90mm at the same time as the Brits were trying to get their own 17 pounder problems worked out for mounting in a turret. Don’t confuse the 90mm with the larger 105mm which was placed on Shermans in the M4A3 105 versions, a.k. the Sherman IVB in the British list.

Both the British and the Americans had seen the need for a more powerful gun in the Sherman, but the Americans also wished to design a new ammo storage system which could be adopted to and retro-fitted into the existing 75mm turret designs to hold down the tendency of the ammo to "brew up" when hit. This precipitated the M4A1 75mm (W) with a wet storage system, this was developed in ’43 and introduced as a stand-alone system in ’44, and also retro-fitted to existing 75mm Shermans which had the dry ammo storage.

And let’s not forget that the Firefly was built on the M4A4 version which is longer in both hull and track length (6") than the non-Lend/Lease Sherman. The huge cumbersome Chrysler mulit-bank 30 cylinder engine required this increase in length, and it also moved the center of gravity further rearward which was a ‘good thing" for the longer barrel of the 76.3mm 17 pounder. And even then it wasn’t a great adaptation, the Brits had to cut a hole in the back of the turret to house the radio, cover it with a steel box made of steel plate, eliminate one crewman, and turn the cannon on its side so it could be loaded and fired by the same man, consequently the firing rate was about half that of the other Shermans with a three man turret crew.

Even then the 17 pounder gun wasn’t a standard 17 pounder, but a special built model for the Sherman application, and the first ones weren’t completed and accepted until early 1944. Which ironically is the date the first M4A1 76mm (W) Shermans were accepted for service with the new M62 turret, which would NOT have accepted the 17 pounder.

The 17 pounder’s projectile of 76.3mm could go 2,980'/sec, but the American 76 wasn’t all that far behind since it could fire a 15.4 lb AP shell at a muzzle velocity of 2,600'/sec. Later, recognizing that this was still too slow, the M1A2 L/55 was introduced, with a muzzle velocity of 3,400’/sec, which could penetrate 158mm of armor at the same distance the Firefly could penetrate 140mm (500 meters).

It isn’t a simple matter of asking the Americans to put the British main gun into the Shermans, it is much more complicated than just "not built here" as well. That may have had something to do with it, but not the entire story.

 

Great reply brndirt1, this was an outstanding post. Fleshed out the facts with excellent commentary.

 

Aside from what has been presented so far, the other reason the US turned down the installation was on the basis of its crudity.

The gun had to be installed on its side to allow sufficent room to load it. Because the gunner on a 17pdr operated the gun from the Left side and in a Sherman the gunner was on the right side of the gun, a series of Rube Goldburg bell cranks and other lash-ups had to be made to allow the gunner to operate the gun controls. These introduced back lash and slop in the system making it harder for the gunner to quickly and accurately place the gun on a target.
The size of the gun and its length in the turret also cut the gunner off from the other half of the turret. This required an additional hatch for the loader to be installed so he had a means of getting in and out of the turret.
Then there was the ammunition supply arrangement. This required removing the hull gunner and replacing him with a portion of the now much larger rounds. The arrangements were deemed unsatisfactory by US ordinance people. I believe that one critisim here was the new ammo bins blocked the floor hatch.
Because the gun was heavier and longer than the 75mm it also had to be counter-balanced with a large lead weight. In addition this change in weight imbalanced the turret making turning it, particularly on any incline, more difficult.

While the "not invented here" syndrome explains part of the problem it was the very real reasons above that made the US ordinance department not want to use the gun.

 

An interesting discussion on another website about the 76mm M1A1 and 17pdr..

Testing of 76 mm Armor pentration - Tanknet.org

 

Nevertheless, on the battlefield, the crude, ugly, kludged-together Firefly could kill a Tiger, when the smooth, sleek Sherman couldn't.

I know which one I'd rather drive.

 

and the 75mm M3 armed Sherman could deal with infantry(armed with Panzerfausts) and anti-tank guns far better then either the 76mm M1A1 & 17pdr . Guess which killed more tanks??? Other tanks??? anti-tank guns??? or Infantry anti-tank weapons? Which armament could deal with enemy infantry better?

 

Allegedly British Fireflies logged very few kills in Normandy because commanders were reluctant to use them in anything but the most dire emergencies (Hart, The Clash of Arms). It probably was not apparent at the time that the 17 pdr. was needed and it might not have been possible to adopt a foreign-made weapon into US armament manufacturing time table if the invasion was to happen according to schedual.

 

Not quite. The US was interested in them but there weren't even enough to fit out the British units at Normandy. Production issues also insured that they weren't going to be produced in any sort of decent time frame in the US.

The idea was to take one of the 90mm turrets from the T series tanks and put it on a Sherman. They had the same size turret ring.

They didn't realize how much they needed it and in any case the M4 had a fighting chance vs German armor and proved it repeatedly.

 

Thanks for the link "ickysdad", very informative. I had another one which described the trouble the British had getting the 17 pounder adapted into both the Sherman and Cromwell (?) turrets. I'll look around for it, the "higher-ups" put the kybosh on further testing at one time, and that delayed even the British getting the weapon into a turret for almost a full year.

 

I don't think it's a fair comparison. The 17pdr had greatly superior penetration properties to the american 76. (140 vs 93 standard ammo, 203 vs 139 rare specialised ammo, all at 500m.) The M1A2 L55 improved this to about 106 standard, 165 specialised.

The American guns using specialised anti-tank ammunition can rival the 17pdr using standard ammunition, true. But these HVAP rounds were generally in very short supply.

For reference, frontal armour of Tiger I is 100mm. The net result is that in the normal combat situation with crews not among the lucky few with special ammo, the 17pdr can kill Tigers and Panthers frontally at 1000m+, while the 76mm must close to 100m, or hope for a side shot. This is a huge difference.

Now you can say that the 17pdr is deficient relative to the 75mm in terms of HE performance, but this doesn't fly when we look at the 76mm - the 76mm was supposed to be a dedicated anti tank gun. But in the end, it fell between two stools by giving a decrease in HE performance relative to the 75mm, but not giving enough of an improvement in AT performance to be justify it. The British did a lot better with mixed 75mm/17pdr units.

Yeah.... but there was a lot of bloodshed they didn't need. A mere fighting chance isn't that much of a comfort to a poor tanker. Fortunately historically the bulk of the tank fighting fell to the British, at least in the early stages.

 

I am not disputing the fact that the 17 pounder in the Firefly had superior ammunition and armor penetration ability. That isn’t my point in the least. I was attempting to highlight the two different approaches to the problem of "anti-tank" guns in Shermans as applied by the two different camps. The British and the American. While taking into account the "tank destoyer" concept which was still holding sway in American armored doctrine.

While the British managed to convert about 2,000 (I’ve seen all kinds of numbers) existing Shermans into the Firefly version before war’s end, after about Feb. of 1944 we Americans produced and mounted about 10,703 examples of the 76mm cannon, out of the 18,873 fighting vehicles produced before war’s end about a year later.

Although tanks with this armament (76mm) were available in early 1944, U.S. troops in Normandy did not receive them until July because of a command decision which stated that it would be better to send soldiers into Europe with weapons they were already familiar with, and that there would not be enough time to train gunners on the new system before the invasion. The first to actually receive the tank with the new armament was, ironically, the Soviet Union who found them satisfactory.

Hero of the Soviet Union, Dmitri Loza, writes in his book Commanding the Red Army’s Sherman Tanks how they performed well on the Eastern Front. Soviet testing against two captured Pz.Kpfw VI Ausf. B "Royal Tiger" tanks showed that the 76-mm M1 could penetrate the Royal Tigers’ side plates at distances 1.5 to 2 times greater than the native Soviet 85-mm gun which became the armament for the famous T-34-85 tank.

As per the Firefly production:

Legend has it that the gun was turned ninety degrees to fit into the turret. Well, it was – and this helped to facilitate left-handed loading. But the problem was much, much more complex than that. The recoil system had to be completely revamped. The cradle for the gun tube had to be modified to fit, and that caused problems in itself because the piece was no longer properly supported. To fix this, the chase (the material that tapers from the breech to the barrel) had to be lengthened through a painstaking manufacturing process. The turret bustle housing the radio had to be extended to make more room.

In addition ammunition for the 17 Pounder was much larger than the ammunition for the 75-mm M3, which means that ammunition storage needed to be rearranged, as did crew accommodations! The turret had to have a new hatch added to facilitate quick escape for the crew due to the bulk of the gun. The bow gun and its gunner, who was also the assistant driver, were wholly deleted to add more space for ammunition.
　
See:

M4 Sherman: Firepower | Socyberty

Now, if it was decided at "command level" that training the crews to operate the only slightly different 76mm models in the up gunned version of the Sherman, I wonder if that little ‘hiccup" might have also come into play as to the dis-interest in the British 17 pounder being used instead of our own 76mm. And having a turret already past the design stage which would accept the 76mm, where it would have been a "back to the drawing board" event for the 17 pounder.

Again, I am NOT disputing the superiority of the British round, nor its cannon. I am disputing whether or not it would have been a "good idea" to make that change on a major scale.

 

I've also heard there was a limited number of 17lb guns available. On the other hand we had a turret already designed that would fit the turret ring of the M4 and mounted a 90mm gun. The problem there was what the additional weight would do to the Sherman and there was no overwhelming need expressed prior to Normandy for it. Again even if the decision were made in late 43 it's not clear how many would have been operational prior to Normandy.

 

Not true.
The fitting of the 17 pdr in a Sherman tank was a last minute modification that only just made it to British Commonwealth tank units in small numbers before D-Day, there was no spare capacity to build Firefly's for the US forces as well. When in early 45 some capacity within the factories producing the modification became available a number of Fireflys were built for the US Army, but the war ended before they saw operational service and the completed Fireflys were returned to the British.

ps, It has been claimed that the 17 modification was only used with the M4A4, this is incorrect. While the majority of conversions were on the M4A4 ( Sherman VC)the M4A1 (Sherman IIC ) and M4A3 ( Sherman IVC) were also used.

 

Yes, I posted that incorrectly, I hadn't seen the other versions as converted. Don't know how I missed them, but do you know at what level the other two models were converted? I was under the impression that the other two were really "minor players".

 

Sherman VC

Sherman IIC

Sherman IVC

Hello Birdirt1
Im afraid I don't have the figure for each model produced, but there is a reference in the Osprey book by Stephen A Hart 'Sherman Firefly V Tiger' which states that 'during the production run increasing numbers of Sherman I or I Hybrid ( M4 and M4A1) chasis(IIC) were used for the conversion instead of the Sherman VC '(M4A4).

ps, The conversion that was used for those planned to go to the US army was mainly the M4A3 (IVC)

 

A question for you more knowledgeable guys. Israel mounted 90 mm main guns in Sherman's then made some with 105's. The 105 was the Chieftain Post War gun, not our short 105. Not trying to bring post war stuff in , just the feasibility of up gunned Sherman's in WW2. I raise it as a question only. they also added a rear turrent bustle not unlike the Firefly.

As for the US not wanting to use a British gun, was not the P-51 up engined with a Packard licensed Merlin of British design? It would appear the US could have licensed build a modified 17 pounder but perhaps by then they were looking at the US 90mm or the 76.. I read, somewhere, that US Ordinance philosophy was for tanks to support infantry and not fight tanks in the beginning. Experience seems to have changed that somewhat . It appears to me that by 1941 standards the US 75 was impressive but slow to up date. Am I correct in my old memory that 76 mm Sherman's were produced at a rate of 25% to 75% 75mm ones ? Was that an Ordnance Corp decision?

My children and I discovered a Sherman at a private museum on the edge of the Ardenne with the floor hatch open and we got quite dirty scrambling in then sat quietly as we had ignored a "Do not climb on tank " sign in French and English. Interesting to sit in one. Years later we discovered two more, one a 76mm, north of Saverne and the other just outside Strasbourg. Both were memorials maintained impeccably by the French. There is a good bit of armor left in that part of the world.

GB

 

That would be the Sherman M-51, which was equipped with the French 105 mm CN 105 F1 gun. However to fit it in, they had to reduce it from 56 caliber to 44, equip it with a large muzzle brake, and develop a smaller cartridge, all to reduce the amount of recoil.

The US Army was expecting great things from its 76mm, but its actual performance was something of a disappointment, but by then they were committed to its production, and to be fair, its later performance with newly developed high velocity ammo was good.

Again to be fair, the main opponents of Allied armour were infantry and A/T guns, and the HE shell fired by the 75mm on a normal Sherman was probably the best of its type.

y

 

Redcoat, I appreciate the better information than I had or remembered, many thanks. I wrote Chieftain but meant Centurion as I assumed that since the Israelis had Centurions they would have used the 105 from them. I always enjoyed going to your tank museum at Bovington.

GB
Alabama

 

My understanding is it was more a matter of not being practical. The Britts didn't have any spare Firefly's and I'm not sure if they had any spare 17lbers. US production would have taken a while to get underway. The US did look at putting a new turret with a 90mm gun in it on the Sherman. I think they could have had it in mass production sometime in the latter half of 44 but the Pershing was on the way and they thought it would be out sooner than it was.