RE: German 75mmL43, L48 and L46 velocities

RE: German 75mmL43, L48 and L46 velocities (Full Version)

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Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/23/2015 4:40:56 PM)
quote: ORIGINAL: Mobius Here it is. [image]local://upfiles/21308/3242F1881BF044A184328185870F046F.jpg[/image] But, I am interested in the 1944 data. We have this data in the 7/42 PaK 40 pdf from the old German doc site. Technically, this was published in the April 1943 version of the document. 1943 saw the general fielding of the PzGr. 7,5 cm projectile in great quantities. The monthly numbers of both Panzer IV with KWK 40 weapons, and Stug III 40, along with Pak 40 towed and SP, probably showed the greatest technical change as far as combat power. Unfortunately for the Germans, they thought they had offensive capabilities on a grand scale. I read that HE rounds were somewhat scarce and the substition of using HEAT rounds was authorized. Please note the HL/A column is blank. My understanding is the HL/B was used during this period. The L43/48 weapons did have PzGr 40 ammunition during this period. The Pak 40 weapons had very little actually.

Mobius -> RE: German 75mmL43, L48 and L46 velocities (9/24/2015 2:37:27 PM)
quote: ORIGINAL: Elron Hubbub Technically, this was published in the April 1943 version of the document. I read that HE rounds were somewhat scarce and the substition of using HEAT rounds was authorized. Please note the HL/A column is blank. My understanding is the HL/B was used during this period. Is the HL/C included in the 1943 document or is just a reprint of the earlier edition?

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/24/2015 3:48:31 PM)
I would have not cut it off it was. I believe you can quickly compare the two and find a glaring difference I have previously stated. In any case, I believe the HL/C introduction was much later in 1943 at the earliest. Here is a early 1944 document for a German used russian weapon. It is dated March 1, 1944. Please note that this is a cardboard one page document, that is supplied to front line units using the weapon, as a training device. Also, note, the Germans were notorious for fielding weapons and supplying manuals, etc. afterwards. The Panther ammunition was manufactured in great quantities before documentation was available. The manuals for the vehicle itself, like the Tiger, came after the troops had them. Given that a weapon such as this is supplied with HL/C in early 1944, I would not be surprised if HL/C was available for other weapons earlier. Note the enemy AFV that are shown in a 1944 document. They are behind the times. Basically, they give hit % also. I doubt aiming at the designated parts of the AFV is worth it over 400 meters. Best to just go for the middle parts and hope for the best. Edit: I read that StuG units in late 1944 reported that HL ammunition was good, but that they still preferred AP in most cases. I would have to assume they meant HL/C given the feedback on HL/B in other reports. [image]local://upfiles/52248/1559D410DC8C4C5D9F51BDA5DFF898CD.jpg[/image]

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/26/2015 4:19:45 PM)
An interesting point is that the cancelled German 7,5 cm L40 weapon, developed before the T34 made the Germans rethink everything, did use the same Pz, Gr. Rot round as the KWK 37 (L24) weapon of the early Panzer IV/StuG III. I can dig up the particulars but it only penetrated roughly 68 mm at 500 meters, and about the same at 100 meters! Its velocity was in the 680 m/s range. Basically, it was pushing the early design 7,5 cm projectile to its limit. This graph shows a very interesting comparison. Note that the graph states that both Pz Gr. 39 for the Panther and KWK 40 and Pak 40 are basically the same. This projectile seems to be the gold standard as far as velocity tolerance. Note that the Pz. Gr. 39 design is actually a two part welded construction. That is, under the cap, the actual penetrator shows the engineering drawing having two slanted lines. [image]local://upfiles/52248/3B567CB6D8534D34A66173E380E5CB85.jpg[/image]

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/26/2015 5:28:20 PM)
armor plate (30 ° inclination tion): 7.5 cm V. 100 500 1000 1500 2000 KWK 37 rot.Pz 365 M/s, 41 39 35 33 30 (mm) 7.5 cm Kan L40 rotPz. 685 65 64 62 59 56 7.5cm StuK. 40 L43 Pzg- Patr 39 740 98 91 82 72 63 7.5 cm StuK. L / 48 Pzgr.Patr 39 790 106 96 65 74 64 At this time, the Pz. Gr. 39 cartridges are loaded with 2.43 Kg of propellant. I really have doubts about the L48 achieving this velocity (790 m/s). Especially since the penetration values are so low. I believe that there is a type error and it actually might be 770 meters a second. The strait physics math would support this. 1/2MV*V

Mobius -> RE: German 75mmL43, L48 and L46 velocities (9/26/2015 6:24:38 PM)
I have that on my website. http://www.panzer-war.com/page43.html The chamber was reduced and the AP cap was made harder and more blunt. The Germans must of took a clue from the blunt nosed Soviet BR-350A shells. I'm not going to say print error or not. I need more evidence.

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/26/2015 6:37:43 PM)
later penetrators [image]local://upfiles/52248/34BAEE2931094D6289F6015FD1518AE8.jpg[/image]

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/26/2015 7:22:58 PM)
quote: ORIGINAL: Mobius I have that on my website. http://www.panzer-war.com/page43.html The chamber was reduced and the AP cap was made harder and more blunt. The Germans must of took a clue from the blunt nosed Soviet BR-350A shells. I'm not going to say print error or not. I need more evidence. Yes, it is unreadable on your website. The Germans "Must" have? I would need more evidence... You linked this website...note the velocity of 750 M/s and the penetration value... http://stugiii.com/sturmartillerie/maingun.html Logic could also be used... Could 10 M/s difference possibly make a 8% difference in penetration? Could 50 M/s difference in be had by lengthening the tube by 14 3/4 inches? Using the same cartridge? It is possible that the early L48 barrels were used. That is, with the progressive twist. These were tossed and constant rate twist was used.

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/26/2015 7:29:11 PM)
BTW, the Pz Gr. 39 differs in length. Since it has reduced the filling, and therefore has more metal (density), it must reduce overall volume. The big difference is the two part core. It might have been a nod to manufacture. It is not easy to get the transition from hard to 'soft' along the body. So, making the front part hard and then welding on the back, while perhaps time consuming, actually pays off in consistancy.

Mobius -> RE: German 75mmL43, L48 and L46 velocities (9/28/2015 2:37:15 AM)
One of the things that concerns me is if the person filling out the technical data sheet just looked up the penetration on a graph like you posted or the one in the BIOS report. (German Steel Armour Piercing Projectiles and Theory of Penetration by British Intelligence Objectives Sub-committee i.e. the BIOS report) [image]local://upfiles/21308/35257E8F171546DBB50DFA0ACEA95144.jpg[/image]

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/28/2015 12:57:42 PM)
It says "no longer produced" in the lower left. I doubt that it was given much attention to detail. 750 M/s? I always thought the 740 M/s often quoted was for the 2.43 Kg powder weight of the first Pz Gr 39 rounds. 750 M/s would be for the later 2.5 Kg rounds (these were produced earlier than I thought). L43 weapon status January 1945... [image]local://upfiles/52248/13AA913EB1B74D5EAA5A4679E023A4F0.jpg[/image]

Mobius -> RE: German 75mmL43, L48 and L46 velocities (9/28/2015 3:32:32 PM)
quote: ORIGINAL: Elron Hubbub It says "no longer produced" in the lower left. I doubt that it was given much attention to detail. 750 M/s? I always thought the 740 M/s often quoted was for the 2.43 Kg powder weight of the first Pz Gr 39 rounds. 750 M/s would be for the later 2.5 Kg rounds (these were produced earlier than I thought). That would make sense.

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/29/2015 2:50:20 PM)
Well, IF it was true, then the longer L48 would almost certainly have a higher velocity. Having the projectile under pressure is how velocity is usually attained. Acording to this guy (see his website), he has info regarding late war testing of both weapons... quote: Well, the difference was'nt that big. In my StuG-Book (coming in English this Year (probably by RZM Imports) I've included a test table of the Armament Office. Test 8.4.44: L/43: Vo 750 m/s, the Pz.Gr.39 penetrated (1000m 60°) 81 mm L/48: Vo 770 m/s, the Pz.Gr.39 penetrated (1000m 60°) 84 mm The tests were performed several times during the war, a decrease of the Vo as effect of the powder quality was obvious. Peter from http://www.historyfacts.biz/en/

Mobius -> RE: German 75mmL43, L48 and L46 velocities (9/29/2015 7:05:27 PM)
Oh boy, more obvious. In English? It must be in German now. I think Yousername somewhere pointed out the L/43 and L/46 barrels were the same length or something to that effect. The Aberdeen data shows the L/43 Vo as 2428 f/s. The L/48 Vo as 2461 f/s. The L/46 as mentioned before as 2598 f/s.

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/29/2015 10:49:10 PM)
quote: ORIGINAL: Mobius Spielbergers Sturmgeschutz book page 64: "On 14 April 1942 results were reported for the test firing which had taken place in Hillersleben on April 3rd. The first gun tested (R V 1), installed in a Sturmgeschutz, had experienced twice failed to eject spent shell cases out of 87 rounds fired, utilizing shelsl that had been warmed 10 to 35 degrees centigrade. " This is, of course, an acceptance test with the temperature of the ammunition cartridges being the variable. The Germans considered 10 deg C (50 degrees F) to be normal temperature. 35 C would be the maximum for normal ammunition. Anything above that would use "Fur Tropen" ammo. Some people posting claim that the high end temp projectiles flew at 820 M/s or some such. In any case, this is not a battle report. In many AFV, temps rise quickly and they have ammunition stored in 'hotspots'. The Elelphant TDs were noted to be hot-boxes with all the engines and generators and electrical motors. Even the Jagdpanzer IV had issues. They eliminated the unneeded auxiliary gas motor since there was no turret, and the space could only be used with a double-walled tub. I would expect that given enough running time, these rounds would get some heat in a steady state.

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/30/2015 12:20:46 AM)
quote: ORIGINAL: Mobius Oh boy, more obvious. In English? It must be in German now. I think Yousername somewhere pointed out the L/43 and L/46 barrels were the same length or something to that effect. The Aberdeen data shows the L/43 Vo as 2428 f/s. The L/48 Vo as 2461 f/s. The L/46 as mentioned before as 2598 f/s. Yes, many grogs in Europe have better access to data it seems. Most are multilingual also. Aberdeen data have a date or Test #, etc.? Or is just strait translation of a German document?

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/30/2015 12:23:25 AM)
quote: the L/43 and L/46 barrels were the same length or something to that effect. Well, then here is a graph that shows what that length barrel would make if we varied the charge...at 50 degrees F. [image]local://upfiles/52248/71DF7F7C94AF40AA80464F91D75EADAC.jpg[/image]

Mobius -> RE: German 75mmL43, L48 and L46 velocities (9/30/2015 12:40:03 AM)
quote: ORIGINAL: Elron Hubbub quote: ORIGINAL: Mobius Oh boy, more obvious. In English? It must be in German now. I think Yousername somewhere pointed out the L/43 and L/46 barrels were the same length or something to that effect. The Aberdeen data shows the L/43 Vo as 2428 f/s. The L/48 Vo as 2461 f/s. The L/46 as mentioned before as 2598 f/s. Yes, many grogs in Europe have better access to data it seems. Most are multilingual also. Aberdeen data have a date or Test #, etc.? Or is just strait translation of a German document? It appears that the 37mm Pak 35/36, 50mm Pak38, 75mm Pak40, and 76.2mm pak36 table ranges are all in yards and penetration values higher than German figures. That is because of the penetration criteria and the armor is normalized to 237 BHN (US standard). German test armor averages 260-280 BHN. But the 88mm Pak43 and 128mm data is a straight conversion of meters to yards and uses German penetration data. Note- I could be wrong and it really is test results though Spielberger has the 88mm penetrating 186mm at 1000m while Aberdeen has it penetrating 186mm at 1000yds. And the US criteria usually results in a higher penetration number than the German. The other tank guns are in a appendix with only muzzle velocity and the penetration at 500yds. and 30 degrees. (Except the 75mm/L48 where there is no penetration data.) (All these have a lot of other data like weight, twists, etc.) You can still find the book. 'German Tank and Antitank' by E.J. Hoffschmidt W.H. Tantum IV at some old book stores.

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (9/30/2015 1:26:35 AM)
I might pick that up for 15$ Ahem...2.69 Kg...776 M/s? One German document show that as the reduced charge for the Pak 40 Pz Gr 39 in 1943. It is interesting that the German reworked Soviet 7,62 cm gun used the Pak 40 cartridge 'brass' and used 2.6 Kg of powder. It had a heavier Pz Gr though. One document claims the Pak 40 also went to the 7 degree constant rifling.

Mobius -> RE: German 75mmL43, L48 and L46 velocities (9/30/2015 4:06:40 PM)
I'm in the process of writing a little program that calculates the ballistic limit per US criteria and the German criteria using the same data. The US formula is defined in a number of tech manuals and is pretty straight forward. It is basically a 50% chance of a 50% full penetration. The German method as defined in the BIOS report seems simple but the example given and results doesn't mesh with the stated method. So it is a little squirrelly. Maybe something got missed in the translation to English?

Ratzki -> RE: German 75mmL43, L48 and L46 velocities (10/1/2015 5:29:24 AM)
Just out of curiosity, what controls headspace in these large cal. guns? Poorly controlled ammunition headspace in a rifle affects accuracy, as well as chamber pressure so I am just wondering if this is an issue here as well.

Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/1/2015 10:42:06 AM)
quote: ORIGINAL: Ratzki Just out of curiosity, what controls headspace in these large cal. guns? Poorly controlled ammunition headspace in a rifle affects accuracy, as well as chamber pressure so I am just wondering if this is an issue here as well. I don't what headspace means. Is it anything like 'jump' or 'barrel whip'?

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/1/2015 6:11:42 PM)
They are rimmed cartridges. They use sliding block to close. The head space is then the thickness of the rim. Any adjustment would then be on the sliding block if any.

Ratzki -> RE: German 75mmL43, L48 and L46 velocities (10/6/2015 1:02:55 AM)
Would in the case that yoiu guys are discussing, could variations be the result of different manufacture of cases with slighth variations depending on where they were produced. I have to be very carefull with lot numbers in reloading rifle ammo.

Ratzki -> RE: German 75mmL43, L48 and L46 velocities (10/6/2015 7:26:37 AM)
Head space is controlled by some part of the case and is what keeps a constant distance between the case and the gun's chamber. In effect, all cases are fire formed to some degree as the case expands inside the chamber which is what seals the chamber so that no pressure is lost during projectile movement down the barrel. If the cases are not consistant then the pressures inside the case and down the barrel can vary which affects accuracy and velocity. Head space is also a projectile alignment tool to make sure that the projectile enters the barrel correctly. Some barrels like things one way yet another barrel of the same calibre can want things slightly different with reguards to headspacing. There just seems to be alot of potential variations that are not known. Even positions of "gas checks" are not consistent between projectiles from the same company. Moving or adding/removing a gas check (I think they are called rotational bands in large calibres) is a huge game changer in velocity. I have had bullet manufacturors provide projectiles with very different gas checks with reguards to position and number. Some have crimping groves, some don't. These all came from the same company with the same style and weight bullets. I think that unless you are using ammo from the same assembly line with all components provided from the same lots and being fired through the same barrel that you are going to have variations in performance.

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/7/2015 3:24:05 PM)
http://www.cruffler.com/trivia-October99.html Hopefully, this can put us all on the same page. The rimmed cartridge is dimensionally critical as far as the thickness and diameter of the rim. The rimless is critical in length diameter etc.

Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/15/2015 4:03:26 PM)
Here's a link to a PDF of what I think is the source of those 1943 German graphs. pretty big. 385M https://www.dropbox.com/s/mzkvkd8wc64c3w8/Vorg--nge-beim-Beschu---von-Panzerplatten-Bericht-166-Lilienthalgesellschaft-1943.pdf?dl=0 Here is a sample of a German test. (I converted 76 Kg./mm2 to BHN hardness.) [image]local://upfiles/21308/8BDACBA4FE584157A23F40D09987C3C3.jpg[/image]

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/22/2015 4:04:15 PM)
That seems to be a collection of research papers dealing with other arms such as naval, aviation, etc. It's good stuff if you can decipher the German of those times. The 3 shot group demonstrates the German method of testing. Shot 1 makes a dent and bounces off (NG), shot 2 is stuck in the plate (NG), and the final shot is a pass through and assumed to detonate inside. In reality, shot 2 would spray a good deal of fragmentation and could cause casualties and damage {edit: I looked at a larger blowup of the photos and it looks like the 2 shot may have actually broke off the welded penetrator piece and that may have entered also}. The Germans increased the velocity till they could get 5 repeatable results. They must have had a test fixture that allowed these high velocities (higher than a L70 weapon), and they used varying charges. The German method seems to be the most stringent of all the combatants. Looking at the graphs, which shows 30 degree test results, one might wonder how a KWK40 or PAK 40 might have success against a T34 frontally. The answer to me is that the T34 has many weaknesses along with its highly sloped armor. Namely the hatch and MG and also shot trap. Combined with results like 2 in the test, the German 75mm weapons could not only penetrate the turret frontally, they could also do good damage to the hull. The Panther probably had it much easier as far as taking out T34.

Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/22/2015 10:34:04 PM)
quote: ORIGINAL: Elron Hubbub The German method seems to be the most stringent of all the combatants. Yes, it is more stringent. I produced a little program to calculate the US Naval Ballistic Limit (V50) and the German Penetration limit. Halfway down the page link to .exe http://www.panzer-war.com/page33.html One additional difference is that the US number if normalized to 237 BHN armor while the German 200mm test armor is 217 BHN armor. quote: ORIGINAL: Elron Hubbub Looking at the graphs, which shows 30 degree test results, one might wonder how a KWK40 or PAK 40 might have success against a T34 frontally. The answer to me is that the T34 has many weaknesses along with its highly sloped armor. Namely the hatch and MG and also shot trap. Combined with results like 2 in the test, the German 75mm weapons could not only penetrate the turret frontally, they could also do good damage to the hull. The Panther probably had it much easier as far as taking out T34. The Russians tested it on the T-34 and it penetrated glacis up to 1000m. http://tankarchives.blogspot.com/2014/04/spare-track-links.html The Yugoslavs tested it and it penetrated up to 1300m. Maybe different criteria. Maybe different muzzle velocity.

Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/23/2015 3:51:53 PM)
The Germans did not use 30 degree in acceptance tests since they could not get the repeatable results that they were stuck on. That is, they 'needed' 5 consecutive shots to penetrate in a condition to detonate the HE filler. In reality, highly sloped armor introduced vaiables that were negligible in a 60 degree test. Not only ricochet but also damage to the base fused HE. Of course, they also consume more test plate since the angled shots need more distance between them. Also, the plate would tend to deform after successive shots. IF we take the 30 degree data above in post 207, AND we assume that the Germans could indeed meet the 5 shot criteria, THEN I would probably be assured that they had a 'slow-crossover' and that there is a range where 2 and 3 and 4 out of 5 are achievable. It is not as well defined a velocity range like the 60 degree test. The Germans are being anal retentive it seems. I also believe that the Soviet hard armor would produce casualty agents even when struck by a projectile that might penetrate but ricochets.

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