jdginaz | 14 Jun 2018 10:54 p.m. PST |
Without context those numbers mean nothing. |
Fred Cartwright | 15 Jun 2018 3:04 a.m. PST |
Mark I have never suggested that the US should have switched to the 17pdr gun. They had made that particular bed and had to lie in it. What they should have done was design a better gun in the first place. As the last article I linked to says in the conclusions you should always design your next generation weapon to exceed the capabilities that you need now. The 76mm gun was designed to combat the threat of what the US was facing at the time the upgunned, uparmoured Panzer IV and the 76mm Sherman produced a tank roughly compatible in performance to the Panzer IV. As for the 76mm gun yes the gun has to be balanced at the trunnions, but there are other ways of doing that than lopping 15" off the barrel. You also have to balance the turret or it won't traverse. The British had to balance the turret on Firefly conversions. As far as increasing MV is concerned it is not quite as simple as bunging in more propellant to increase chamber pressures. First the breech has to withstand the higher pressure. Second the propellant has to be fully burnt before the round leaves the barrel or the extra is wasted. Finally the pressures generated have to be sufficient so the round is being accelerated for the full length of the barrel, bearing in mind that the volume behind the shell is constantly expanding as the shell travels down the barrel. If the force on the shell drops too much then shell slows due to the friction with the barrel. All that means there are practical limitations to the MV you can produce for a given length of barrel. Given an optimised shell a longer barrel will produce higher MV's than a shorter one. It is my understanding that the main problem with 17pdr barrel wear came from the sabot round. |
Legion 4 | 15 Jun 2018 6:36 a.m. PST |
Warning there is a lot of maths in it. Or math as you Americans say! Lots of math … I'm done … I'm out ! |
thomalley | 15 Jun 2018 7:05 a.m. PST |
From June 6, 1944 through May 15, 1945 for US tank and tank destroyer losses in the European Theater of Operations, United States Army (Western Front): around 7,000 (including 4,295–4,399 M4 tanks, 178 M4 (105mm howitzer), 1,507 M3 Stuart tanks and 909–919 tank destroyers, of which 540 M10 tank destroyers, 217 M18 Hellcat and 152 M36 tank destroyers). An American studies states that based off a sample of 12000+ Allied tank casualties from all theaters of WWII 54% of casualties were the result of gunfire. "Gunfire" includes tanks of course, but also includes AT Guns, StuGs, other SPGs, and artillery pieces. The second biggest percent is AT mines at 20%. Noncombat reasons(being stuck in the mud, mechanical breakdown, etc.) was the 3rd highest cause at 13%. The figure of 13% is probably low. The Canadian Army and USMC recorded "more accurate" percentages of 25% to 40% of casualties attributed to noncombat reasons. Hollow Charge weapons like the panzerfaust 7.5 %. The remaining 6.5% was everything from mortars to aircraft to satchel charges. Further in the article there is a chart that shows British losses by type. 14.5% from enemy tanks and another 24.5 from assault guns/TD. Must remember the Allies were attacking and not always in good tank country. Of course the German will have similar numbers, probably a lot less mines, but will have losses from the air. |
Legion 4 | 15 Jun 2018 7:44 a.m. PST |
Those are some high losses … But the US could replace most of them. The Germans not so much. Very few at best … |
Marc33594 | 15 Jun 2018 8:16 a.m. PST |
Mark is correct on the specifications. Once again, from Hunnicutt, page 198: "…To shorten the development cycle, the projectiles for the standard 3 inch gun M7 were adopted for the new weapon. The powder charge in a smaller diameter cartridge case was adjusted to obtain the same 2600 ft/sec muzzle velocity as the 3 inch gun." As a result of feedback improvements were made to the standard M1A1 76mm. Page 206: "…Based on the test program, it was recommended that all 76s be equipped with muzzle brakes. When the end of the barrel was threaded for a muzzle brake, the M1A1 was redesignated as the 76mm gun M1A1C. A later model, designated as the 76mm gun M1A2, differed in having rifling with a tighter twist. Rifling in the M1A2 made one turn in 32 calibers while that in the M1A1 turned once in 40 calibers. The tighter twist improved projectile stability producing a slight increase in penetration performance at the longer ranges. All of the M1A2 guns were quipped with muzzle brakes." |
jdginaz | 15 Jun 2018 1:26 p.m. PST |
The Canadian Army and USMC recorded "more accurate" percentages of 25% to 40% of casualties attributed to noncombat reasons. That statement is odd and doesn't necessarily corollate. The Marines were using the Sherman with the diesel engine under very different conditions. I'm not sure but I think the Canadians were also using the diesel engine too. |
mkenny | 15 Jun 2018 2:05 p.m. PST |
a tank 'Casualty'is any tank unable to fight.It is a not a 'total loss'. Allied tank casualties during the breakout from Normandy rose to levels near that of the Germans. |
Marc33594 | 15 Jun 2018 3:00 p.m. PST |
The Marines transitioned to the M4A3 when production of the M4A2 was switched over from the 75 to the M4A2(76). However the Marines were not above holding on to whatever they could so the M4A2 75 could still be found fairly late in limited numbers. I won't argue with the fact it was under very different conditions :) |
Legion 4 | 15 Jun 2018 3:06 p.m. PST |
A Diesel engine is much less prone to catch fire when the vehicle is hit & KO'd. Petrol/MoGas is not a very good option … |
jdginaz | 15 Jun 2018 7:51 p.m. PST |
A Diesel engine is much less prone to catch fire when the vehicle is hit & KO'd. Your kidding Right? It's been proved over and over again that what kind of fuel was used had zero effect on whether a tank burns or not. Think on these two points, where are tanks hit the most the front half or the back half? Then, at the temperatures involved when a tank is penetrated it wouldn't matter what fuel was used if it is in the way it will ignite. |
thomalley | 15 Jun 2018 7:52 p.m. PST |
I think the argument is that the Marines and Canadians kept better records. |
jdginaz | 15 Jun 2018 9:40 p.m. PST |
Probably less argument and more assumption. |
Legion 4 | 16 Jun 2018 6:59 a.m. PST |
Your kidding Right? It's been proved over and over again that what kind of fuel was used had zero effect on whether a tank burns or not. Think on these two points, where are tanks hit the most the front half or the back half? Then, at the temperatures involved when a tank is penetrated it wouldn't matter what fuel was used if it is in the way it will ignite. Hey, that is what I was told a number of times … Think about this … when we were taught to make a "Molotov Cocktail". You fill the container(usually a glass [wine] bottle) with 2/3 oil/diesel. Then 1/3 MoGas, leaving the neck empty for the fumes to gather. Tie gas soaked rag around neck. Light & throw … BOOOOOooom ! The fumes from the gas cause the "explosion" catching the oil on fire. And the oil spreads and burns more slowly that pure MoGas. I've also seen a gas stove on a Mobile Kitchen Trailer blow up. For what must have been from a gas leak(?). Looked like a small "nuc" blast ! The MKT was a total lost. Don't think that probably would have happened if it was diesel. What is the difference between a diesel and gas engine ? Basically a Spark Plug … note the "spark" … Diesel burns differently than MoGas or even Kerosene … Another thing … why were the versions of M4s that used MoGas were called "Tommy Cookers" … ? Quote all the studies you like … I'm just telling what we were taught. And what I saw … But you and/or the studies you reference may be correct ? |
thomalley | 16 Jun 2018 8:54 a.m. PST |
Yet we hear no complaints about Germans gas engines. Though with their shortage of fuel its interesting ( I think it was too costly) that they never used diesel. |
Wolfhag | 16 Jun 2018 9:17 a.m. PST |
The Germans were making gasoline from coal. Coal hydrogenation produced high-quality aviation and motor gasoline, whereas the F-T synthesis gave high-quality diesel and lubricating oil, waxes, and some lower quality motor gasoline. The two processes actually were complementary rather than competitive, but because of only coal hydrogenation produced high-quality gasoline, it experienced much greater expansion in the late 1930s and war years than the F-T synthesis, which hardly grew at all. Gas shortage was one of the reasons for the drive to the Caucasus in Russia. PDF link Wolfhag |
Mobius | 16 Jun 2018 11:34 a.m. PST |
Mark, where did you find the PDF that had this chart?
Could I have the link please. |
Mark 1 | 16 Jun 2018 1:49 p.m. PST |
Hmmm. Posted a similar reply, but then it disappeared. If it re-appears, apologies for making y'all read it twice. Mark, where did you find the PDF that had this chart? pictureCould I have the link please. Steve - Sorry, but I don't have a link. I've had the doc for years, and I'm not really sure how I came upon it originally. The PDF includes cover letters (from a colonel at Ordnance to the Commandant of Archives at the Command and General Staff School at Leavenworth) which indicates it was a secondary distribution (providing 20 copies to the school). The PDF also includes a scan of the cover of the folder indicating which index box it was from in the archives (N-5590.14 in case anyone is interested). Only after all of that stuff does the PDF get down to "Data for HVAP Ammunition for 76mm, and 3-inch Guns, Office of the Chief of Ordnance, May 1945". That last piece, the actual content, is also marked (on the last scanned page) with an Archives Index Box number N-9512. This tells me that the same materials (the core data) may be available in two places in the National Archives. It's possible that I scanned it myself when doing research in the National Archives. It is my style to scan the cover of the folder. But the fact that it may have appeared in two places, as well as the cover letters, makes me think this scan came from materials from the Command School at Leavenworth. That's not stuff I was ever chartered to research at the National Archives. But lots of Leavenworth stuff is available from the Leavenworth website itself, so its possible I got it there. Blah blah blah … ok, so I don't know a link to give you. But I'd be happy to send you the PDF. I don't have your email anymore, having deleted any emails more than 10 years old (!). So if you'd like to PM me your addy, I'll send you the PDF PDQ. Least I can do for you … still not even with you for the copy of Bird & Livinston's WW2 Ballistics that you so generously gave me. -Mark (aka: Mk 1) |
Mobius | 16 Jun 2018 2:07 p.m. PST |
You will have to decode this. So my email is exdx AT sbcglobal DOT net The pdf looks a lot like the PDF on the 90mm gun N-9950.3. PDF link |
Marc33594 | 16 Jun 2018 2:34 p.m. PST |
"Another thing … why were the versions of M4s that used MoGas were called "Tommy Cookers" … ?" All M4s were referred to by that. The issue, as it later turned out, had nothing to do with the fuel but ammunition storage. Fires, and explosions, dropped dramatically with the adoption of the so called "wet" stowage models which saw the ammunition stored lower in the tank. And M4s were no better or worse than other tanks as far as this goes. There were more of them, used by a variety of nationalities, so more likely to see one go off. |
Mobius | 16 Jun 2018 2:48 p.m. PST |
Tanks with diesel engines caught fire and exploded as well. It was because the fuel tanks were hit. When they were not full but had 15-25% fuel penetration would explode the tank. link |
Mark 1 | 16 Jun 2018 7:03 p.m. PST |
You will have to decode this…. Well hopefully I decoded it correctly. Look for a present in your inbox. The pdf looks a lot like the PDF on the 90mm gun N-9950.3. Yep. Very similar. I have that one too. But notable in that particular Ordnance publication is how much effort they went to to let everyone know they had tested the 90mm AP ammo against the armor of REAL German tanks. I have not seen that in other Ordnance reports. My reading is that there were a few shock waves after the Isigny tests (and Eisenhower's letter), and the boys at Aberdeen got the message. BTW I also attached another report: "Tank, Heavy, T26E3 and related vehicles, January 1945, Office of the Chief of Ordnance". Just for your leisure time reading pleasure. ;) It includes the basic information on the various developmental (experimental) versions of the T26 (original T26 through T26E5), and gives some data on the the more powerful T15E2 90mmL70 gun used in the T26E4 version. Thought you might find it interesting. -Mark (aka: Mk 1) |
Mobius | 16 Jun 2018 9:24 p.m. PST |
Thanks, Mark. What is curious is the different elevation settings for the variety of gun mountings. It says they all have the same terminal velocity at the same range but different elevations have to be used. Different elevations should indicate different ballistics but it seems it doesn't. So something else is in play. Maybe gun jump. |
Legion 4 | 17 Jun 2018 7:02 a.m. PST |
Yet we hear no complaints about Germans gas engines. Tanks with diesel engines caught fire and exploded as well. It was because the fuel tanks were hit. When they were not full but had 15-25% fuel penetration would explode the tank. Thank you for the information. I may be wrong about the M4, German AFV fuel, etc. Regardless an AFV is generally full of things that go or can go boom …
All M4s were referred to by that. The issue, as it later turned out, had nothing to do with the fuel but ammunition storage. Fires, and explosions, dropped dramatically with the adoption of the so called "wet" stowage models which saw the ammunition stored lower in the tank. And M4s were no better or worse than other tanks as far as this goes. There were more of them, used by a variety of nationalities, so more likely to see one go off. That makes sense … But again … Regardless an AFV is generally full of things that go or can go boom … So generally being in or around them can and should make you a little "cautious" … They don't have to blown up or shot at you to be "dangerous" … they can just run you over … |
Mark 1 | 20 Jun 2018 11:05 a.m. PST |
What is curious is the different elevation settings for the variety of gun mountings. It says they all have the same terminal velocity at the same range but different elevations have to be used. Different elevations should indicate different ballistics but it seems it doesn't. So something else is in play. Maybe gun jump. Been noodling this in the background for a couple days. As I read it, the different settings are for the 76mm gun (same versions) in TDs vs. in M4 tanks. So … It may well be that the sites were set differently, based on the primary role envisioned for the vehicles. A tank was expected to fire a lot of HE. A TD was not. Perhaps the site settings optimized for HE needed different offsetting for HVAP than the site settings optimized for AP. It may also be that the M4 tank had a periscopic gunsite as it's primary site, while the M18 had a direct co-axial gun site. Offsets may well have been different just due to the need for angular convergence in one vs. the other. Just some thoughts. I don't have any analysis to back them, so all grains of salt apply. -Mark (aka: Mk 1) |
Blutarski | 20 Jun 2018 12:57 p.m. PST |
Trunnion axis height may be the culprit ….. B |
Neroon | 20 Jun 2018 9:10 p.m. PST |
So something else is in play. Maybe gun jump. Good guess, but do you understand why? Let's review: same gun (with or w/o muzzle brake), same projectile (HVAP), same sights (M71D), same mount (all my refs say M62 for both Sherman and Hellcat), and same recoil force. So what's different? The chassis. To be precise it is the weight of the vehicle. 72000 lbs for the Sherman vs 40000 lbs for the Hellcat. A heavier vehicle will (all else being equal) always be a steadier gun platform because it is better able to absorb the recoil shock (aka chassis rocking on its suspension) than the lighter vehicle. Force vs Inertia – simple physics. Thus we see from the chart that the M18 w/o muzzle brake is less accurate than the M4 w/0 muzzle brake, but the M18 with muzzle brake is more accurate than the M4 w/o muzzle brake (due to reduced recoil force). If the chart were extrapolated to include the M4 with muzzle brake it would be more accurate than the M18 with muzzle brake (same recoil force but greater weight -> higher inertia -> more stable -> less gun jump). Cheers
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Mobius | 21 Jun 2018 6:07 a.m. PST |
Thanks to World of Tanks forum someone found the jump of these guns.
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Lion in the Stars | 21 Jun 2018 3:23 p.m. PST |
Yeah, the WoT guys get way lost in the details sometimes. Especially considering that the game tweaks the hell out of the stats. |
Mark 1 | 25 Jun 2018 11:05 a.m. PST |
Yeah, the WoT guys get way lost in the details sometimes. Especially considering that the game tweaks the hell out of the stats. Quite agree that the game is so tweaked that the historical basis is almost unrecognizable in the game. And BTW the same is true of World of Warships and World of Warplanes. But I would not say they get "lost in the details". Rather, they start from the details, and then navigate their way to mass market appeal. Yes, you can find tanks called T-34 or Panther in the game, and the 3D models look like T-34s and Panthers. I mean, they REALLY look like T-34s or Panthers. With a LOT of care put into knowing were every bolt should go. OK, so some basis in historical fact. But … T-34s carrying 76.2mm F-34 guns are almost NEVER seen in the game, and Panthers are pretty weak and pathetic compared to the other tanks in their tier, so not exactly a good track to the actual history of those names. But … They do an amazing amount of high-quality historical research as the underpinning of those games. What goes in is solid historical information. What comes out is all that is necessary to make the games successful as games. Those among us who actually care about the history of tanks (or warships or warplanes) should be grateful. Because Wargaming (the corporate parent) is funding more and better research on 20th Century military history than any university, model/miniature manufacturer, museum foundation, publishing house, national military historical branch or philanthropist I know of. There are more than 150 MILLION players of their game titles. Even if you only get 2 or 3 dollars a month per average player from sales of stuff in the premium store, when you have a store with 150 million customers you have a certain ability to get stuff done. You can get some insight into their decision making by reviewing their corporate core values. One of their five core values is: "EVIDENCE: Our team makes decisions off research, analytics and data to make our players happy, wherever they are." That's the key. You can almost read it as a flow. Do the research, and then study what gamers want and bend reality around to keep Chinese and Russian and North American and British and French and German users happy, so they keep playing. But start with the research. Which they do. And which we (or at least I) benefit from. Go Wargaming! -Mark (aka: Mk 1) |
Mobius | 25 Jun 2018 12:49 p.m. PST |
You are right in that they have a lot of resources. But, what I get out of their forum is that it is their 150 million users that find historical things and post them rather than WOT themselves. Maybe WOT funds websites that also do research. In this thread we have the PDF on 76mm HVAP PDF link Funded by the US. For some reason they could not find their own TM 9 1907 copy that had tables on 76mm HVAP. But it is in the July 1948 edition. (Maybe they thought there was only one edition.) link Or also in, part_2 which has 76mm HVAP graph as well. p 161 link |