Penetration of .375 H and H at std and quick twist.

andrewctillman

Beginner
Feb 6, 2013
225
1
PENETRATION OF FMJ RN BULLETS IN 375, 416, AND 458 CALIBER RIFLES AT STANDARD AND ENHANCED VELOCITY AND ROTATIONAL VELOCITY.

C 2001 Andy Tillman





Boards Caliber Bullet Velocity Twist Shots/Comment

458 x 404 (Similar to 460 GA).

71 1/2 458 x 404 500 FMJ 2,367 fps 1-10 One to two more boards than 1-14 twist which had slightly higher velocity.

71 1/2 458 x 404 500 FMJ 2,367 fps 1-10

48 458 x 404 450 GSFN 2,450 fps? 1-12 Perfectly straight bullet path.

46 458 x 404 500 FMJ 2,334 1-10 Hit left edge. Exited side of stop-box. Tipped at 40 boards (13 more than 1-14 twist). Penetrated 10 boards more than 1-14 twist. Threw wood 30 feet!

28 458 x 404 500 Barnes X 2,334 1-10 Unstable. Expanded and turned 180 degrees. Fully sideways at 23 boards, traveled base forward until 28 th. Climbing (upward) wound profile like 5.45 x 39mm.



Note: this is photographed from the back side of the 28th board. The long, unstable bullet turned over 180 degrees and traveled base forward.

450 Ackley

70 1/2 450 Ackley 500 FMJ 2,400 1-14 1-2 boards less penetration than 1-10 twist.

69 1/2 450 Ackley 500 FMJ 2,400 1-14

36 450 Ackley 500 FMJ 2,400 1-14 Exited side of stop-box. Tipped at 27th, fully sideways @ 31 boards. Ten boards less penetration than 1-10 twist.

458 Winchester (BRNO 602 with 25 inch barrel).

62 Simulated 458 Winchester 2,030 1-10 (Down-loaded 458 x 404). Penetrated 3-4 more boards than standard twist.

59 458 Winchester 500 FMJ 2,021 1-14 Circa 1980 Remington/FMJ

58 458 Winchester 500 FMJ 2,105 1-14 Federal Premium/FMJ

39 ½ 458 Winchester 450 GSFN 2,050 1-12 Simulated 458

23 458 Winchester 510 RNSP 2,105 1-14 Expanded. Federal Premium.

21 458 Winchester 510 RNSP 2,021 1-14 Expanded. Circa 1980 Remington.

416 x 375 Improved (Similar to 416 Remington or Hoffman but with 1-10 twist).

71 416 X 375 Imp 410 Kynoch FMJ 2,400 1-12 Three shots. Very consistent performer. Kynoch is copper clad steel jacket like Hornady.

375 Improved (Similar to 375 Weatherby or 375 JRS), 22 ½ inch barrel.

71 375 IMP 300 FMJ 2,791 1-8

70 375 IMP 300 FMJ 2,791 1-8

50 375 Improved 300 FMJ 2,791 1-8 Exited side of stop-box. 13 more boards than standard twist that exited.

375 H & H (22 inch barrel)

65 375 H & H 300 FMJ 2,570 1-8 Penetrated 4 more boards than standard twist.

61 375 H & H 300 FMJ 2,570 1-12 Twice

37 375 H & H 300 FMJ 2,570 1-12 Exited side of stop-box.

NOTES:

Stop-box made from 12 x 12 inch square sheets of ¾ inch thick pine spaced ¾ inch apart.

Range, 25 yards

All FMJ bullets were copper clad steel jacketed Hornady unless noted otherwise. The Kynoch had a slightly more rounded meplat than the Hornady.



QUICK ANALYSIS:

A faster than normal rate of twist in both 375 and 458 caliber rifles at both standard and “improved†velocity levels resulted in 3-4 more pine planks being penetrated than at standard 1-14 or 1-12 rates of twist.

Rotational velocity was not as important as increased velocity. The 458 wildcats (2,400 fps) penetrated 10-12 more boards than the standard 458 Winchester. The 375 improved (2,800 fps) penetrated 6 more boards than the 375 H & H.

A very high rate of twist (1-8) resulted in a penetration gain of 4 more boards over a standard 1-12 twist in the standard velocity 375 H & H.

Rotational velocity of greater than 1-10 twist may be beneficial when using monometal bullets of high SD. These very long (1.6 inch) bullets may also benefit from careful design, keeping the center of gravity exactly the same as its center of form.

There does not appear to be such a thing as a “magic†velocity threshold of 2,400 fps as some observers have suggested. The 375 improved at 2,800 fps penetrated 9-10 more boards than at 2,570 fps.

No increase in penetration was noted using contemporary versus vintage 458 Winchester ammo. When loaded with the same 500 gr Hornady FMJ bullets, circa 1980 Remington 458 Winchester ammo actually penetrated one more board than higher velocity Federal premium ammo loaded in 2001.

Most bullets could be de-stabilized by an edge hit on the 12 x 12 inch boards, or an overlapping hit on previous shots.



The quicker twist bullets were somewhat more consistent than slower twist but not enough shots were made to verify this with absolute certainty.

When FMJ bullets did exit the side of the stop box, the quicker twist did so 10-13 boards later than the standard twist.

A 458 Winchester could have the same rotational velocity as a 450 Ackley just by using a 1-12 twist.



ROTATIONAL VELOCITIES TESTED:

1-14 @ 2,021 fps = 1,717 revolutions per second (rps).
1-14 @ 2,105 fps = 1,789 rps.
1-14 @ 2,400 fps = 2,040 rps
1-12 @ 2,050 fps = 2,050 rps
1-12 @ 2,400 fps = 2,400 rps.
1-12 @ 2,450 fps = 2450 rps
1-12 @ 2,570 fps = 2,570 rps.
1-8 @ 2,570 fps = 3,855 rps.
1-8 @ 2,800 fps = 4,200 rps.

Additional tests.

I also tested some unconventional .458 caliber solids and FMJ Flat Nose bullets and thought you all might like to see how they did in the La Grange stop box. (3/4 inch thick plywood spaced 3/4 inch apart in a rigid stop box).

Range 20 yards as that is what the late George Hoffman told me he used since, "That was the range that a charge was likely to develop."

450 Dakota, 1-12 (not standard 1-14) twist.

Reference standard, 500 gr Hornady FMJ RN, 2,397 fps chronographed, 70 boards.

450 gr Barnes RN solid, 2,555 fps, 62 1/2 boards.

400 gr Barnes RN solid, 2,676 fps, 54 boards.

450 gr North Fork Flat Nose (2nd generation with slight radius on meplat), 52 1/2 boards.

450 gr GSFN, 2,524 fps, 47 boards. this expanded to .431 diameter meplat and tipped and yawed from about 33 boards, to about 45 degrees.



500 gr Kodiak FN bonded with hard lead core, 2,407 fps, 33-43 boards. This expanded to .65 caliber!!!! Shot it twice and expanded the same each time. Tore the shit out of the boards like a soft point.

To put this into perspective, a 375 will do 61 boards, and a 458 Win mag will penetrate 58-59 boards with Federal screaming premium FMJ (2,105 fps from 25 inch BRNO 602 barrel).



Interesting that the 375 with 300 gr FMJ and the 450 Dakota with a 450 gr RN at similar velocity and SD had same penetration.

The FN rather than RN bullet profile takes 15% or ten boards off the 450 gr bullets penetration. Probably worth it for the increased tissue damage.

The 450 gr bullet has about 10% less penetration than a 500 grain. Not bad.

The 400 gr. has about 25% less penetration than a 500 gr.

Just for laughs I shot the 7.62 NATO into the stop box and it went 22 boards and was recovered base forward, turning 180 degrees at 14 boards. Those head shots on jumbo must really be all or nothing!
 
Very good information.
Pretty interesting to learn that the faster spin rate gives deeper penetration.
Thank you for posting.

JD338
 
Quite exhaustive testing. Fascinating information, to be sure.
 
The pictures assuredly add punch to the presentation. Thanks for posting them.
 
Back
Top