Flaws in Russian WW II BR 471 Velocities

[Miles Krogfus]

WW II Russian firing tests published incorrect information on various AP and APBC projectiles. For example, the 122 mm BR 471. A late 1944 firing test against a Tiger II listed the BR 471 and the BR 471B as having the same velocities at range, as at 2500 meters, 653 m/s for the BR 471 and 653.6 m/s for the BR 471B. Also the BR 471: 759.3 m/s 700m, BR 471B 771.1 m/s at 500, 641.9 m/s at 2700 m, 602.3 m/s at 3400 m. A 1944 #144 T
Firing Table gave the BR 471 with a 800 m/s muzzle velocity the same speeds per range as the 122 HE also with 800 m/s mv. Thus the BR 471 was incorrectly assumed to have these figures: 794 m/s at 100 meters, 770 m/s at 500 m, 741 m/s at 1000 m, 712 m/s at 1500 m, 684 m/s at 2000 m, 656 m/s at 2500 m, 629 m/s at 3000 m.
A 1969 Russian FT #144 T corrects confusions. Its figures for the 800 m/s mv BR 471 are: 200 m 770 m/s, 500 m 733 m/s,1000 m 670 m/s, 1500 m 612 m/s, 2000 m 558 m/s, 2500 m 509 m/s, 3000 m 464 m/s.
Thus the ranges that this AP could supposedly penetrate WW II Panzers during firing tests are incorrect. Likewise for the BR 471B, that was not used in WW II combats because of the assumed performance of the BR 471. It has the actual speeds at the above ranges (in meters per second): 779, 756, 718, 681, 646, 611, and 579 m/s at 3000 m.

[Contender]

The DDR document has it slower than that:

BR-471 (122mm L/43 D-25T)
200m:756 m/s
500m: 715 m/s
1000m: 655 m/s

Your numbers seem to fit the AT piece:
BR-471 (A-19 122mm L/46)
200m: 776 m/s
500m: 738 m/s
1000m: 676 m/s

[Miles Krogfus]

I used these Russian firing tables: the 1938 edition for the #144 1931 Corps Cannon 1931, the 1944 2nd edition #144 T Supplemented, for the Model 1943 (A-19 S) and 1944 !22 SU (D 25 S), and JS II Tank gun Model 1943 (D 25), and the 1969 #144 T (D 25 T) for my post. Could you post the muzzle velocity and velocities at 1500, 2000, 2500 and 3000 meters for the DDR firing table of the A-19?

[Contender]

Sure
A-19:
1500m: 617 m/s
2000m: 561 m/s
2500m: 509 m/s
3000m: 461 m/s

[Miles Krogfus]

The 1969 corrected muzzle velocity of the D-25 T gun was 795 m/s with a 5933 mm long barrel (L 48.33). The D-25 barrel was 5840 mm (L48) and the 1931 and 1931/37 models of the A-19 field artillery 5650 MM (L 46.3). Without a muzzle break as a field gun, the A-19 barrel was shorter, but had more muzzle velocity than all JS 122 mm tank guns with their muzzle brakes. Lacking its muzzle break, the D 25 barrel measured 5240 mm (L 43).

[Mobius]

WW II Russian firing tests published incorrect information on various AP and APBC projectiles. For example, the 122 mm BR 471. A late 1944 firing test against a Tiger II listed the BR 471 and the BR 471B as having the same velocities at range, as at 2500 meters, 653 m/s for the BR 471 and 653.6 m/s for the BR 471B. Also the BR 471: 759.3 m/s 700m, BR 471B 771.1 m/s at 500, 641.9 m/s at 2700 m, 602.3 m/s at 3400 m. A 1944 #144 T
Firing Table gave the BR 471 with a 800 m/s muzzle velocity the same speeds per range as the 122 HE also with 800 m/s mv. Thus the BR 471 was incorrectly assumed to have these figures: 794 m/s at 100 meters, 770 m/s at 500 m, 741 m/s at 1000 m, 712 m/s at 1500 m, 684 m/s at 2000 m, 656 m/s at 2500 m, 629 m/s at 3000 m..

To visualize the differences between the WWII error ballistics and the correct ballistics I produced the following graph.
The table at the right of the graph is from the WWII BR-471 data above using the G1 Gâvre drag table with a ballistic coefficient of 4.778 at an elevation of 615 ft.

[Mobius]

Likewise for the BR 471B, that was not used in WW II combats because of the assumed performance of the BR 471. It has the actual speeds at the above ranges (in meters per second): 779, 756, 718, 681, 646, 611, and 579 m/s at 3000 m.

I do have some problems with above BR-471B Firing table numbers.
The above data also works for the BR-471B when the MV=795 m/s.
From Archive Awareness

So can't be 718 m/s with both MV. Can it?

Then the DDR tables which also appear to be pretty authentic have a bit of a problem. Or at least one of the tables has a problem.
While the BR-471B the MV=781 m/s, the Impact vel. @3000m = 584 m/s. It only takes a 781m/s BR-471B shell 4.2 seconds to go 3,000m while a 795m/s shell of the same type 4.4 seconds.

[Peasant]

Another possibility is that both A-19 and D-25T had exactly the same ballistics, but someone took the first velocity that appears in the table for it's default round, which is not AP but rather HE, and quoted it as the gun's muzzle velocity, from where this error became the most often quoted value for this gun.



And, although one shouldn't use anecdotal evidence in matters like this, my experience with soviet military tech suggests they wouldn't adopt two very similar guns with slightly different ballistics at the same time(unlike germans). If it wouldnt've been possible to increase the muzzle velocity of D-25T to match that of A-19 they would rather reduce the propellant load of A-19, especially since it's less critical for firing HE.

[Mobius]

I don't want to post the firing table again but here is a bit of it.
viewtopic.php?f=47&t=219251&p=1988317&h ... 1#p2042842

[Mobius]

Peasant posted links to original updated Russian gun documents.
viewtopic.php?f=19&t=241618&p=2200555&h ... m#p2200555

[Mobius]

There were errors in Firing Tables of 152mm ML-20 gun/howitzers.
Peasant posted links to a report on 152mm ML-20 gun of 1937 and updated and released in 1944.
https://mega.nz/#!zeYWXSRD!l23BKTeGcH-H ... v4-El5cKrY

This has a partial firing table of the BR-540 APHE shell without striking velocities but with time-of-flights. These look to be impossible numbers as the ToF for the first 500m is the same as from 1500-2000 meter. In effect the shell does not lose velocity in its first 2000 meters. This report has a penetration table based on the DeMarre formula of the standard K=2400 type. Solving for velocity using this table gets some unbelievable numbers as well.

There a 1943 report of the 152mm ML-10 updated and released in 1968.
https://mega.nz/#!fW4G0Yqb!1o8rMzFEg0iM ... YWiva1h_hk

This has a firing table of the BR-540 APHE shell with striking velocities as well as realistic time-of-flights. So this appears to have corrected values.
The ballistics of the BR-540 shell for both guns should be virtually the same except the MV of the ML-20 is 600 m/s while that of the ML-10 is 560 m/s.
The penetration values would have to be calculated from corrected striking velocities.

152mm BR-540.jpg

[Peasant]

I bring good news. Recently I've got my hands on the "Service manual for the 122mm self-propelled gun D-25S" and the following part explicitly listing all the differences between this gun and the 122mm artillery gun Mod.1931/44. Among them, the muzzle velocity at full charge for D-25S is listed as being 781m/s. compared to 800m/s for the field piece.



And since both D-25S and D-25T have the same length of rifling and are operating at the same pressure we can safely assume that they both would have the same muzzle velocity.

If you want to see the whole document yourself, here is the link: http://www.pirochem.net/books/voennoe-d ... u1946.djvu

[Mobius]

And since both D-25S and D-25T have the same length of rifling and are operating at the same pressure we can safely assume that they both would have the same muzzle velocity.

If you want to see the whole document yourself, here is the link: http://www.pirochem.net/books/voennoe-d ... u1946.djvu

The first seems to be missing pages while the latter links to cosmetics.

[Peasant]

And since both D-25S and D-25T have the same length of rifling and are operating at the same pressure we can safely assume that they both would have the same muzzle velocity.

If you want to see the whole document yourself, here is the link: http://www.pirochem.net/books/voennoe-d ... u1946.djvu

The first seems to be missing pages while the latter links to cosmetics.

I did upload only the relevant pages, since I've assumed you already had the FT for the D-25T gun I've posted here: viewtopic.php?f=19&t=241618
About the second one, I dont know, works fine for me. Do you have an adblocker installed? Maybe some ad is redirecting you or smth. I've re-uploaded the document on my cloud disk, shouldn't be any problems now: https://mega.nz/#!qDBxFYqL!RBVy5mMREBdl ... q9b7IckiRM

[Mobius]

OK. thanks I got it. I was hoping for a firing table.