How truly effective was the US M1 76mm gun?

I believe all fin stabilized MTB guns are smooth bores. The only current main gun I am aware of is the British 120MM Challenger 1 and 2. The current defense forums and articles give it an edge in accuracy but it is expensive to make and subject to more wear. RPG's btw are fin stabilized . Someone correct me but are not our depleted uranium projectiles bit fin stabilized and fitted with a sabot as they are clearly sub-caliber.

Back to WW2 I am not aware of a fin stabilized gun in production nor as a experiment but I may well just be uniformed. hope so as it would be interesting. I always found the German tapered bore rounds most interesting but that is another topic.

Back to the US 76 mm. it has been discussed a good many times here as having a less effective HE round. I am yet to be convinced that a 76 with the same effectiveness as the 75 could easily been produced by using a slower burning powder to achieve similar velocity. The less effective 76 mm round was one argument against switching from the 75, germane to this thread.

 

GT, the Germans experimented quite a bit with "Pfeil" (arrow) rounds, which were fin-stabilized. Most were intended to stabilize extended range artillery rounds and so forth. Not sure what the US and British experiments were like.

WRT the HE capability of the American 76mm, it was a problem similar to the HE round in the 17-pdr. Initially they were simply HE projectiles grafted onto the same cartridge, which resulted in excessive Mv affecting fuze operation and effectiveness. The 75mm was liked because of the well-known characteristics of its ammunition and lower Mv. It could be used in "grazing fire" where the 76mm round would simply bury itself before exploding. Further, the 76mm and 17-pdr produced a massive muzzle blast and flash, obscuring target sensing and making accurate second round hits problematic. It was so bad that initially it was recommended for the Medium Tank M4 76mm that the TC dismount and move to the side before firing to sense rounds (I think more sensible thinking prevailed before that idea went too far).

The Germans solved the problem to their satisfaction by producing a separate HE round for the 75mm Pak/Kwk 40 and Kwk 42 with a lower propellant charge and interchangeable reticules for the different types in sighting. The British and Americans eventually came up with similar solutions.

 

Rich, Thanks for the information about the German's attempt to stabilize artillery rounds, funny, I started to post above if anyone had tried it in WW2 it probably would have been the Germans. Spring loaded fins in a rifled tube sounds like a difficult thing to solve....maybe it was.

There is a thread on this forum, I am not good at finding them, about the 76 and the HE problems including velocity and sights. . Kodiacbear and I concluded the velocity could be lowered by a change in powder to reduce velocity or adding combustionable fillers to exsiting powders and several solutions for the sights were discussed. It appears the Allies were a bit slower to develop such. funny how short comings always outlast fixes in memory !

Hopefully some can recall that thread. Welcome to the forum, you have good insights and information to offer.

Bit off topic but you may have an answer. Most WW2 high velocity cannon had muzzle brakes but no MBT of today that I am aware of does. They have smoke evacuates and thermal sleeves and hit 5000 fps but no brakes. they blast must be severe., especially the Leopard 2's L55.

 

AFAIK, the recoil absorbers/retarders are much better today then they were back then.

Muzzle brakes were only dabbled with when trying to fit the big guns onto the light weight wheeled vehicles.

 

1. The argument that the 17 Pdr was too inaccurate to be useful is nonsense, to use the most polite term. The artillery argument is far from fallacious. The zone of the 17 Pdr was such that 50% of rounds would fall within an area somewhat larger than the average tank at 1500m. Firing a lot of times at the centre of mass would not guarantee a hit, but the numbers would favour a hit sooner or later. Probability works like that , as do destruction shoots,by medium or heavy artillery.

This retrospective justification of the US Army decision not to deploy the piece ignores common sense, the track record of the piece in action as well as the psychological impact on own troops and the enemy that there is a weapon against otherwise invincible tanks. It is a shabby argument to explain why the US Army committed its armoured troops into battle in the main operation of the war without weapons capable of defeating the enemy's heaviest tanks. What is more important is the lack of appreciation by the WW2 US Army for the psychological factors which made an army effective. This latter isn't a trivial matter.

Here is a page from the Tiger Tank manual with one of a series of comforting charts that reassures the Tiger crew that they can KO a Sherman with impunity up to 2000 yards as long as they turn a corner or frontal armour. http://www.esatclear.ie/~godot/ShermanChart.jpg That chart would be nothing as reassuring if the Sherman was armed with a 17 Pdr.!

Note that the panzer Inspectorate did not include esoteric arguments about the accuracy of the tank armament at any of these ranges. Presumably they did not think their soldiers would would be reassured by the argument that "they cant hit an elephant at this distance"

2. There were only enough M10s fitted with the 17 Pdr to issue 12 to each of the two corps Anti tank Regiments which landed on D Day and 12 to each of the armoured divisions. This was due to an industrial dispute in the manufacturing plant. During the Normandy campaign the 17pdr equipped M10s seem to have been introduced as replacements when they became available. I cannot find any evidence for re-equipping units systematically with the 17 pdr version. Nor does there seem to be any difference in nomenclature, certainly not by the artillery staff at army level. They were 17 pdr M10 s as opposed to M10s .

These are the figures for penetration by the new (APDS) Ammunition in the pre D Day notes of BRA 2 Army.
a. 6 Pdr 4000 fps 118mm @30 deg
b. 17 pdr 3950 fps172 mm@ 30 deg
c. 77mm 3675mm 149mm @ 30 deg

.

 

1. I understand that...if you are talking about the 17-pdr firing APCBC, which was just marginally less accurate than the most accurate round fired, the 76mm HVAP. The problem with the 17-pdr APDS was its first round hit probability over 800 yards was poor and it was found that first round hits won most tank engagements. Furthermore, early APDS suffered from gross real world dispersion greater than the estimated dispersion as published. The random scatter of 17-pdr APDS versus APCBC has been calculated as 2.2 times greater at 1000 yards, 1.04 yards versus 0.47 yards. That means if 17 pdr APDS was fired at a 2.19 yard high target at 1000 yards and the range estimation and thus gun elevation was perfect, about one-third of the shots would miss due to random scatter. WO 291/238 states "the wide scatter of 17 pdr APDS makes accurate second shot correction difficult, since the first shot might be based on an accurate range estimate but the wide dispersion could cause a high shot that suggests a long estimate". Furthermore, the combination of faulty design of the "petal" sabot, faulty manufacture (the 4th lot proofed at Woolwich resulted in a 13 by 14 foot shot pattern), muzzle brake interference, rapid fouling of barrels from the aluminium sabot, and the impact of barrel wear meant that the supposed percentage figures distributed by RAC on 28 December 1944 were wishful thinking.

I might agree with you if that was the argument I made. However it wasn't. I always appreciate it when counterarguments are made to arguments I actually make. Tha actual assessment, by US Army Ordnance AND British Ordnance was that 17-pdr APDS had serious accuracy problems that compromised its effectiveness at ranges much greater than around 800-1000 yards. That is why the recommended "solution" - signed off by both American and British observers at Isigny - was mating the US HVAP projectile with the 17-pdr cartridge. Unfortunately it wasn't a practical solution. OTOH, given that average combat ranges in the ETO were 850 yards, realistically the 17-pdr APDS "problem" was mitigated by the fact it rarely needed to attempt hits at very long ranges and could be used at ranges it was effective at.

I am not sure BTW how an assessment made jointly by American and British officers, or the assesment made by AORG would be considered "chauvinism" in a "pro-American" sense? Unless the chauvinism coming out is of the pro-German "invincible tanks" variant? Nor, after investigating most of the relevant documents dealing with tank losses for both the British and American armies, do I believe I have a "disdain" for their experiences.

Just exactly why also BTW would the Americans chose to go through the trouble of manufacturing a British 3" as a subsitute for their own existing 3" and change over the ancillary ammunition manufacture as well when there was so little evidence of a substantive difference until the head-to-head tests that first occurred in May (IIRC) 1944? Hindsight is wonderful and all that but...

Yes, it would have been nice, but it would have been just as nice if the strictures against increased chamber pressure and higher Mv in the 3"/76mm had been eased, and if the reheat treatment of American APCBC rounds had been undertaken before the results of service experience revealed the problems in manufacture (prescience anyone?)

I am sorry, but the Germans also made fatal mistakes based on a lack of sufficient experience. For example, they also found their 8.8cm APCBC performing much worse than expected against Soviet armor in 1941 and 1942 and also discovered the root problem was insufficient final heat treatment during manufacture.

Sadly, if Sedgwick was being fired at by 17-pdr APDS at 2,000 yards I suspect his words would have been gospel.

What do you know? I found my data. (Curses of moving, nothing is ever where you remeber it is.)

The SP batteries in the corps and armored division AT regiments were intended to be at least partly equipped with M10 SP carriages converted to carry 17-pdr guns, which became available at the beginning of May. “It was decided that this gun should be issued to complete 50% of unit S.P. equipment in all regiments in Second Army and in First Canadian Army, followed by issues to the Armoured Replacement Group and to the Polish Armoured Division. By 31st May twelve equipments had been issued or were in transit, to each Armoured Divisional and Corps Anti-Tank Regiment in the two Armies, and issues to the Armoured Replacement Group were in hand” (The National Archives (UK) (TNA) WO171/155 – Appendix ‘A’ to R.A. Branch Headquarters 21st Army Group War Diary May 1944). The result was that the corps AT regiment was initially equipped with 12 M-10, 12 M-10 17-pdr and 24 17-pdr. (towed). Each of the antitank batteries in the assault divisions was equipped with eight 6-pdr and four M-10 3” SP guns. TNA WO171/155 – Appendix ‘A’ to R.A. Branch Headquarters 21st Army Group War Diary May 1944. However, unlike the other assault divisions 3rd Canadian apparently grouped all four of its M-10 troops under the 105th as a “Composite” battery. It appears that the 105th Battery’s two troops of towed 6-pdr guns arrived on D+1 after which the regiment returned to its normal organization. See TNA) WO171/155 – Appendix ‘A’ to R.A. Branch Headquarters 21st Army Group War Diary May 1944 and WO171/234 – Second Army Landing Tables

I Corps: 62nd Antitank Regiment RA with 246th and 247th Battery (17-pdr towed), 245th Battery (M10 17-pdr) was attached to 3rd British Division, 248th Battery (M10) was attached to 3d Canadian Division.
XXX Corps: 73d Antitank Regiment RA with 195th and (196th) Battery (17-pdr towed), 198th Battery (M10) and 234th Battery (M10 17-pdr) were attached to 50th British Division.

In most documents related to NEPTUNEthey are referred to as either "M10 17-pdr" or "M10", with the "M10" being the unaltered 3" version. In similar fashion, it was usually "Sherman 17-pdr" or "Sherman" at this time.

Cheers!

EDIT: finding more bits I squirrelled away.

WO 291/238 AORG Report No.256 "The Importance of Gun Dispersion in A.P. Shooting"
6pdr APCBC dispersion at 1000yds...................5.2mins 44yds
75mm M3 APCBC(M61) dispersion at 1000yds 2.2mins 14yds
75mm Mk.V APCBC dispersion at 1000yds........3.0mins 18yds
76mm APCBC dispersion at 1000yds.................1.4mins 14yds
17pdr APCBC dispersion at 1000yds..................5.2mins 64yds
17pdr APDS dispersion at 1000yds....................12.0mins 285yds

WO 291/751 AORG Memo No.427, 24th Nov 1944, "Comparative Dispersion of Tank Guns"
Probability of a hit when firing for effect on a target 2' high by 5' wide (M.P.I. assumed on centre of target) at
.................................................. 500yds; 800yds; 1000yds; 1500yds:
Churchill IV 6pdr APCBC 150rnds......74% 73% 62% 42%
Churchill IV 6pdr APDS 90rnds..........74% 50% 37% 20%
Sherman 17pdr APC 100rnds............88% 66% 52% 32%
Sherman 17pdr APDS 40rnds...........42% 21% 14% 7%
Comet 77mm APC 40rnds.................98% 86% 76% 53%
Sherman 75mm M3 APC M61 150rnds..100% 96% 90% 73%
Sherman 76mm APC M62 40rnds..........100% 100% 96% 92%

EDIT2: and this one:

WO 291/1263 and WO 165/135 dated 22 September:

First round hits obtained by 17-pdr-armed Sherman tanks:

400 yds
APC hit 90.5%
APDS hit 56.6%

600 yds
APC hit 73.0%
APDS hit 34.2%

800 yds
APC hit 57.3%
APDS hit 21.9%

1000 yds
APC hit 45.3%
APDS hit 14.9%

1500 yds
APC hit 25.4%
APDS hit 7.1%

 

Perhaps just a nitpick but I feel an important one. My understanding is that the finding was "The tank that fired first was more likely to win the engagement. Due to the fact that most tankers only took that first shot when they were in an advantageous position."

Alternatively, if you had said "The first round that penetrated was likely to win the engagement" I would certainly agree with you.

 

I tried to find the exact quote...I thought it was in ORO T-117, but I haven't found it yet. IIRC the actual quote was more similar to yours. I'll see if I can track it down in the mess my files are in.

 

I've seen that many times, though like you I don't recall where it originates. The theory I've read differs in that the first shot is the ranging shot and also a shock to the tank on the receiving end. So, while the tank that has been shot at is in a panic to return fire as quickly as possible, the first shooter has his ranging shot and is making corrections to make the hit with his second shot. Only hits count and the first shooter (even if he misses) now has your range, while the target is still one step behind and considerably shaken up as well.

 

Oh, its in any number of ORO and AORG reports postwar that looked specifically at data on tank engagements - Ronnie Sheppard worked on a number of them IIRC - but its the specific quote I recall that I can't find, which is annoying.

 

Looking through a PDF "Tank Gunnery" a summery of US Army official recommendations concerning tank equipment and training based off of crew surveys in 1945. http://usacac.army.mil/cac2/cgsc/carl/eto/eto-053.pdf

The report states that the Sherman 105 HEAT round was capable of penetrating the Panthers Glacis but due to inherent inaccuracy the maximum range was considered as 500yds.

As I peruse this report it gets better and better. It answers some questions that have been brought up in previous threads.

Why didn't they create a 76mm HE shell with a lower velocity but more HE?

 

Yep, what they said...they 'splained it a lot better than I could.

 

This thread caused me to look up when I joined the forum, 2008, cannot believe it. One of my early post, being an old benchrest shooter was about tank main gun accuracy, about which I was very curious. Most discussions were about penetration, projectiles, armor but little on accuracy. This thread has been a revelation to me, much data on just that, accuracy. I have often wondered about sabot separation and how it affected hit probability. even separation seemed difficult as was [passage through the brake. I cannon imagine fouling of the bore by aluminum was horrendous. !!

Thanks for all the information guys, new things to study. On the subject of ranging shots it seems I remember that a 20mm Polsten cannon was mounted on the early 17 pdr Centurions in 1945
. I recall someone writing they were for ranging shots before firing the 17 pdr.. That would seem to imply a very close trajectory. But more recently IO saw where it was not mounted tied to the main gun.

Gaines

 

There was a detailed discusion of this on one of the other forums a decade or more ago. May have been tank net. As I recall a lot of the 17lb'er problems came from one factory (there were three). I don't remember all the details though. I did get a chance to later work with one of the primary contributers though and was impressed by his contributions in both cases.

 

I do not say that I endorse, or entirely endorse, the US Army's objections to the 17 pdr, I am just reporting that argument. In any case I believe that late in the NWE campaigns the US Army in the ETO overcame its objections sufficiently to attempt to obtain its own Fireflies, though the project did not come to fruition before the fighting ended. The various reports on accuracy that have come to light here are very interesting and have told me some things I didn't know.

 

Well, the major "objection" was "we already have a tank-mounted 3" gun so why do we want another?" However, immediately following the initial armored encounters in Normandy, along with the shortcomings of the 3" and 76mm revealed in the three tests of May, July, and August, Bradley requested a crash program for building Sherman 17-pdr for US forces. However, a number of problems intervened.

1). The standard British conversion utilized the Medium Tank M4 and M4A4. Most of those available had already been converted or were no longer in production. So the modification scheme would have to be redesigned.
2). By early September 1944, American forces in the ETO were already suffering a tank shortage, requiring the imposition of a reduced TO&E, so withdrawing tanks for conversion wasn't an option.
3). The modification required the resources of an arsenal to accomplish, which had other fish to fry.

The end result was the matter was dropped by October 1944. However, in the aftermath of the Ardennes Offensive, the idea was raised again and a program was begun to convert 160 American tanks to 17-pdr. The initial 80 were drawn from Continetal stocks with the remaining 80 coming from new shipments from the US. However, only 100 were completed and 20 were turned over to the British.

Cheers!

Rich

 

I'll just drop into the discussion to say that anyone who wants to delve deeper into the Firefly story should beg, borrow or steal a copy of Mark Hayward's book, 'Sherman Firefly' published by Barbarossa in 2001. It's a real enthusiasts' labour of love and answers many, many questions about an important WWII AFV.

 

Thanks for the suggestion, Martin!

 

That's a pleasure - one of the mysteries of WWII publishing is why the Firefly ( along with the PzKw III ) is relatively overlooked ......Mr Hayward's book looks likely to remain definitive for some time yet.

 

Yes, Mark's book is by far the definitive text. Sadly it has been long out of print and even more sadly his webpage now is only accessible via the Wayback Machine.