Some of you have been waiting for the results of my test of 458, 416 and 375 fired from barrels with different rates of twist.

Until I have confirmed publication from one of two magazines, I will probably not post the entire report on the net, but here is the "short course."

Target array was 3/4 plyboard spaced 3/4 inch apart. range 25 yards.

458 x 404, 500 hornady FMJ at 2350 fps at 1-10 twist pentrated 71 1/2 boards.

416, 410 Kynoch FMJ at 2400 fps, 1-12 twist, 71 boards.

450 ackley, 500 hornady FMJ at 2400 fps at 1-14 twist penetrated 69 1/2-70 1/2 boards.

458 winchester from 1-10 twist, 2030 fps, 62 boards.

458 winchester 1-14 twist, 2,021-2,105 fps, 58-59 boards (1980 Remington and 2001 Federal Premium from 25 inch barrel).

375 h & h, 1-12 twist, 2570 fps, 61 boards.

375 h & h, 1-8 twist, 2520 fps, 65 boards.

375 improved, 1-8 twist, 2,800 fps, 71 boards.

Conclusion.

All of the bullets could tumble and exit stop box if an edge hit or overlapping hit on previous shots was made.

The quick twist barrels would exit from 10-13 boards later than the standard twist when this happened. A quick twist does help a bullet "buck brush."

A quick twist increased penetration of the 375 and 458 winchester by about 5-8%.

The 416, 450 ackley, and 458 x 404 (460 GA) had enough velocity and increased rotational velocity, to make dramatic increases in penetration without a quick twist, though the quick twist did help on edge or overlapping hits.

there does not appear to be a magic 2400 fps threshold after which penetration drops off as suggested by Mike LaGranges tests. This was almost certainly due to the 460 weatherbys 1-16 twist.

The 300 gr 375 FMJ continued to penetrate as well as a 416 or fast 458 up to 2,800 fps at 1-8 twist.

However, there is a point where the pain does not justify the gain!

Also tested the premium soft points in 5 gallon water buckets. Best penetration from 400 gr Barnes X. (Lowest frontal area).

Andy

Andy,
I know you are being a bit sketchy with details due to plans to publish this elsewhere, but you do seem to verify the better penetration of the faster twist bullets even at slightly lower velocity in some cases.

This would seem to support the faster twist barrel for dangerous game where that extra pentration might be handy.

The all-around rifle intended for longer range work would have to deal with over stabilization effects on accuracy also. this suggests related tests at long range for the .375 in particular.

The common wisdom of late has been that there is no such thing as a good brush bucking bullet. Maybe that is just a function of inadequate twist rates in the common rifle using heavy for caliber loads? A corrrectable malady: Use more twist.

Another interesting question for me is the 12 twist versus the 8 twist 375 H&H. Was that the same load in the two guns that gave 2570 fps with the 12 twist and 2520 fps with the 8 twist? Or did you have to work up separate loads to get those two different velocities near to each other? Even at a slightly slower velocity it penetrated 4 more boards with the faster twist.

I am also gratified to see that the penetration improved with faster velocity, for solid bullets, I assume. That would tend to put to rest the old bunk about penetration getting no better after the magic 2400 fps threshold is passed.

I will be anxiously awaiting a fuller accounting in publication.

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Good huntin' and shootin',
RAB

RAB,

In the physical world as we know it there is no such thing as "over stabilized" anything. Any body that is moving is either stable or unstable, it cannot be "more stable". In the case of bullets, there is usually a range of twist rates that will stabilize a given weight and length of bullet at a given velocity. Faster twist rates and/or higher velocity will continue to keep that bullet stable as long as it is super sonic. Slower rates of twist can lead to instability if the velocity is not high enough to impart enough RPM to keep the bullet rotating around it's center.

We've been making barrels chambered for the .300 Ultra in 14 and 15 twists specifically to shoot the 150 and 165 grain bullets. At the Ultra velocities with light bullets, it doesn't take as fast a twist as as we have been led to believe. Conversely, I'm shooting a 6MM with a 6 twist with the thought of using 137 grain bullets. The bullets are on order and I decided to try and shoot some lighter bullets. Forget 58 grainers but 70 through 107 perform just fine. They are not over stabilized. Just stable.

My apologies for being pedantic.

Bill

RAB,

I tested every bullet available in 375 h and h in 1981 from point blank out to 500 yards in 100 yd incriments in both a std 375 with 1-12 and my own fast twist 375 (1-8) in the 375 improved. Way over stabilized but they shot up to two minutes flatter at long range due to increased stability when down loaded to std 375 velocity. so there are two features to accuracy. Drop, wind drift, mirage, and actual dispersion. A well made bullet will handle the increased rotational velocity, the average or poor ones wont. Alot of data on this now from national match rifle courses using 69 match bullets vs 62 gr military bullets in the 1-8 and 1-7 twist 223.

You are a careful reader. The lower velocity of the 375 at 1-8 was due to the fact that I shot std 375 ammo in my improved chamber and this looses about 50 fps as it fire forms into the larger capacity case.

The std 375 ammo was a charge of WW 760 that gave about 2600 fps in a 25 inch barrel, and 2570 fps as I recall in my freinds cz550 with 22 inch. My imporved 1-8 also has a 22 1/2 inch stainless, and that is why the vel was slightly less but still gave more penetration.

The BIG PICTURE is that using a 1-10 twist 458 winchester you get as much or more penetration as a 375 h and h. That is a USEFUL increase in penetration with NO DOWN SIDE as to recoil or weird ammo.

Any of you guys building custom rifles take note.

(I can hit a 5 gallon bucket at 500-600 yds with my 1-8 375 improved). Accuracy is OK.

Andy

Elephant hunters:

The fast big bores are penetrating about 53 inches of wood.

How thick is an elephants skull from the side?

From the front?

thanks, andy

Bill Tompkins,
There is a case to be made for "bullet over-stabilization" by ballisticians. This would keep the bullet nose up due to gyroscopic forces instead of allowing the bullet's long axis to track along parallel to the parabola of the trajectory at long ranges where there is a significant upward angle of fire and corresponding angle of descent. At 1000 or more yards the effect is important, so they say. At what range the effect comes into play, I do not know.

That said, I am all for the faster twists.

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Good huntin' and shootin',
RAB

Andy,
Apparently "over stabilization" is not a factor in 5 gallon bucket shooting at 600 yards.

I will always go for a faster twist if I can.
My 510 JAB throws a 750 grain Hornady A-Max at 2150 fps from a 1 in 10" twist barrel, with 1/2 MOA accuracy at 100 to 300 yards, from a benchrest. I have sat out in a cow pasture with a bipod and hit a 24" square, 925 yard distant target reliably, and occasionally in the black. I used a mildot scope and held 5 mils high to do it.

If the 458 Winchester had been produced with a 10 twist barrel it would be more widely appreciated today.

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Good huntin' and shootin',
RAB

RAB,

This really should be the headline for my quick twist study.

How to make a 458 winchester penetrate as well as a 375?

Just give it a 1-10 twist.

No increase in recoil. No reloading hassles. No custom agents asking you what a 458 Lott is?

Just spin it faster.

Wish I had a 470 nitro in 1-20 and 1-10 to test!

I suspect alot of the fishtailed and bent FMJ's on the old English doubles wre due to their 1-30, 1-20 and 1-16 twist.

Andy

Andy,
Your results are very reasonable and similar to some observations in the field.
The 25 yard is still a distance where the bullets are not totally "asleep" and we can observe the influence of the twist and length of the bullet.
The Greenhill formula is very useful for stability calculations with small calibers (6mm), but I think it is not correct for the bigger ones. The formula indicates very high stability numbers even for a .458 in 1:16 twist, but we know the problems.
Your comment on the fishtailed and bent older bullets is absolutely correct. Most are recovered from final shots at very short distance.
The thickness of an elephants head varies considerably, but 48" broadside and 60" length is a good estimate. Only the faster bigger bullets are penetrating fully (.458 500 gr 2400 f/s).
For a more detailed discussion we have to remind, that the mechanism of penetration are different in plywood and tissue, evtl. a bit similar in bone.

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Norbert,

Thank you very much. What twist is your 450 Ackley?

Andy

Andy,

1 in 12, that is my recommendation for .458
normal bullet size.

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I haven't any experience with brush bucking in a .458 but I can add this to RAB's query:

My brother told me that an article he read a while back described the .340 Wby as the best brush bucker tested (against what calibers and through what "brush" I don't know). Apparently heavy, fast, and fast twist all help. However, from personal experience I can state that its nothing to get excited about or count on. I missed an impala because my 225 gr TBBC burned a twig en route. My brother had a similar experience with his .300 Win Mag. The 200 gr X-Bullet hit the warthog (which was 15 yards away) but it was already several inches off the aimpoint and fully sideways by that time, leaving a keyhole lesion in the skin and tumbling lengthwise without expanding.

A bullet in flight is a free body and any unbalanced force acting on it will divert it from its course (its the glancing blow on a slender limb that gets you). But I was amazed how much that could be.

Andy,
I noticed that your 458x404, at 2350 fps penetrated about the same as the .416
I encountered the same thing using a .458 Lott at 2350 and a 410 gr fmjs om tje /416 Hoff. They were within an inch of each other...The 458 bullet will have a larger frontal area hence will slam an elephant somewhat harder, but with more recoil to boot. I never found that I needed any more though, than the .416
George