Flaws in Russian WW II BR 471 Velocities

Discussions on the vehicles used by the Axis forces. Hosted by Christian Ankerstjerne
Peasant
Member
Posts: 249
Joined: 16 Oct 2018 17:21
Location: Italy

Re: Flaws in Russian WW II BR 471 Velocities

Post by Peasant » 27 Feb 2020 12:42

I came up with an easy way of converting "effective distances" reported in soviet testing with the 122mm BR-471B shell(using HE shell ballistics) into real distances for BR-471B shell fired at 781m/s.

distance(m) = reported distance(m) * 0,8 - 300, thats it. For example, 2000m distance reported would actually be 2000 * 0,8 = 1600; 1600 - 300 = 1300m.

Of course this is an approximation but it works extremely well for distances up to 3000m.

Peasant
Member
Posts: 249
Joined: 16 Oct 2018 17:21
Location: Italy

Re: Flaws in Russian WW II BR 471 Velocities

Post by Peasant » 29 Mar 2020 14:31

Another source confirms that D-25T/D-25C are supposed to have a bit lower muzzle velocity than the 122mm corps gun A-19/A-19C:
Source: https://digitalcommons.unl.edu/usarmyresearch/165/

Image

Peasant
Member
Posts: 249
Joined: 16 Oct 2018 17:21
Location: Italy

Re: Flaws in Russian WW II BR 540 Velocities

Post by Peasant » 29 Mar 2020 15:34

Mobius wrote:
08 May 2019 18:06

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
Mobius, I cant believe I haven't noticed this before, but that firing table is NOT for the armour piercing shell BR-540 but for the "БронеПрожигаюший" БП-540 shell aka the HEAT shell for this gun. Its mass and external ballistics are much different.
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.
About that...

Image

Image

The ballistics for this shell are far too good for a sharp tipped shell without windshield and are much closer to BR-412B and other shells of this type than to sharp tipped shells without windscreen.
One explanation I can think of would be that they've used the ballistic model for BR-540B shell to calculate these penetration tables.
Last edited by Peasant on 29 Mar 2020 16:12, edited 1 time in total.

User avatar
Mobius
Member
Posts: 543
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

Re: Flaws in Russian WW II BR 540 Velocities

Post by Mobius » 29 Mar 2020 16:06

Peasant wrote:
29 Mar 2020 15:34
Mobius wrote:
08 May 2019 18:06

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
Mobius, I cant believe I haven't noticed this before, but that firing table is NOT for the armour piercing shell BR-540 but for the "БронеПрожигаюший" БП-540 shell aka the HEAT shell for this gun. Its mass and external ballistics are much different.
I discovered that when I entered it in my ballistics program from the pdf links you provided. From a ML-10 table the MV=560 m/s BR-540 has a striking velocity of 305 m/s at 3000 m. Yet working from DeMarre the striking velocity calculated of the BR-540 from the penetration value of the ML-20 MV=600 m/s is 447 m/s at 3000 m. That is quite a big difference.

User avatar
Mobius
Member
Posts: 543
Joined: 12 Jan 2005 20:45
Location: Glendale, CA

Re: Flaws in Russian WW II BR 540 Velocities

Post by Mobius » 01 Apr 2020 21:12

Peasant wrote:
29 Mar 2020 15:34
The ballistics for this shell are far too good for a sharp tipped shell without windshield and are much closer to BR-412B and other shells of this type than to sharp tipped shells without windscreen.
One explanation I can think of would be that they've used the ballistic model for BR-540B shell to calculate these penetration tables.
My opinion as well.

Return to “The Ron Klages Panzer & other vehicles Section”