12,7x99 AP M2

[Wiedzmin 420]

have question about 12.7x99 AP M2 cartridge  WWII time books gives muzzle velocity for AP M2 - 895 m/s for 45in barrel, modern days firing tables and manuals gives 856 m/s for 45in barrel, which is correct, or both correct but 1st for WWII and 2nd for modern dayes cartridges ?

[Ramlaen 1,410]

It's possible both numbers are correct and they fall within the standard deviation.

 

The place I see 856 m/s listed also states that is 78 feet from the muzzle.

Edited November 15, 2018 by Ramlaen

[Wiedzmin 420]

FT.50-H-2 3 Cartridge, AP, M2 Muzzle Velocity, 853.4 M/S  

Remaining Velocity

 

0 Meters -  853 M/S  

100 Meters - 813 M/S  

1000 Meters - 482 M/S

 

is there any FT on .50 AP M2 that gives 895m/s and remaining velocity on range ? I found only WWII era  schedule but...

[Sturgeon 4,015]

On 11/15/2018 at 8:40 AM, Wiedzmin said:

have question about 12.7x99 AP M2 cartridge  WWII time books gives muzzle velocity for AP M2 - 895 m/s for 45in barrel, modern days firing tables and manuals gives 856 m/s for 45in barrel, which is correct, or both correct but 1st for WWII and 2nd for modern dayes cartridges ?

 

Too big a difference to be instrumental vs. muzzle velocity. Likely 895 m/s is a misprint. I am not sure any M2 AP has been made since WWII.

[Wiedzmin 420]

5 hours ago, Sturgeon said:

 

Too big a difference to be instrumental vs. muzzle velocity. Likely 895 m/s is a misprint. I am not sure any M2 AP has been made since WWII.

pic from some forum, and it gives 2935 f/s for AP M2 

[Sturgeon 4,015]

I'll look into it.

[Wiedzmin 420]

On 11/18/2018 at 2:55 PM, Sturgeon said:

I'll look into it.

any progress ?:)

[Sturgeon 4,015]

37 minutes ago, Wiedzmin said:

any progress ?:)

 

Oh. Yes. Thanks for reminding me. It appears the velocity discrepancy is due to barrel length. The 895 m/s figure is for the 45in barrel of the M2 ground variant, while the 865 m/s figure is for the 36in barrel of the aircraft variant (AN/M2 and AN/M3).

[Wiedzmin 420]

5 minutes ago, Sturgeon said:

 

Oh. Yes. Thanks for reminding me. It appears the velocity discrepancy is due to barrel length. The 895 m/s figure is for the 45in barrel of the M2 ground variant, while the 865 m/s figure is for the 36in barrel of the aircraft variant (AN/M2 and AN/M3).

FT.50-H-2 3  - infantry firing table for 45in + i have US specs on AP M2 cartridge which gives 853m/s IIRC 

[Sturgeon 4,015]

1 minute ago, Wiedzmin said:

FT.50-H-2 3  - infantry firing table for 45in + i have US specs on AP M2 cartridge which gives 853m/s IIRC 

 

I can't tell you exactly why one source or another has a given set of numbers. Sometimes they are just wrong, especially field manuals.

For the record, FM-23-65 gives the muzzle velocity as 2,930 ft/s.

[Sturgeon 4,015]

...And then TM-43-0001-27 gives 2,810 ft/s instrument velocity, so who knows.

[Sturgeon 4,015]

TM 9-1904 (1944) gives the same 2,930 ft/s figure that appears to be representative of 45in barrels (page 210).