Anyone know if the 60 grain partition will stabilize in a 14 twist at 3000fps?

mjbgalt-

The calculator at jbmballistics.com says it won't be stable.

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--Bob

Thanks

Yep, unstable. It would require a minimum of around a 1 in 11 twist rate for said bullet and velocity combo... I got the same exact stability rating, as bullshooter, of ".885", using the Berger twist rate stability calculator..

Berger twist rate calculator

It won't at 3600+ even at 4000 feet above sea level in my part of Montana. Oh, it'll land point-on, but it won't group very well.

Have gotten much better accuracy with the 60 Partition in faster twists, including 1-8. If I recall correctly, it was originally designed the .223 Remington's then-standard 1-12 twist.

Why do they even make 1:14 or 1:12 twists? My 1:7.7 match barrel stabilizes 80 grain bullets and shoots the light ones with no degradation in accuracy that I have noticed.

Because the saami drawings say 14 twist so the unimaginative manufacturers just do it that way i think

Indy,

Because back in the day, jacketed bullets weren't particularly well-balanced, and in faster twists shot less accurately--and the faster you pushed them, the worse they shot.

Which is exactly why so many early rifles chambered for "high velocity" centerfire cartridges had slower rifling twists and often featured relatively short, blunt bullets: They shot more accurately.

This started to change only in the last couple decades. Nowadays even very light bullets will shoot very accurately even in very fast twists.

What could go wrong?

Likely not, but a fella never knows until he tries. Long time ago I had a Hornet that loved Sierra 52 gr boat tail spitzers. And a .358 Win w/ 16” twist that was fond of 250 gr FB spitzers. Everyone said they wouldn’t shoot.

SAAMI does not include twist-rate in their cartridge drawings.

In one of the special "Varmint" editions from Wolfe, Stan Trzoniec reported very good accuracy from a Browning Low Wall Hornet like the one I have with 50gr bullets of some sort. Always thought those were 1-16", but have heard others say they're 1-14". No plans to try them, just interesting.

SAAMI drawings I see do include twist specs. The Hornet is 16” on page 62.

https://saami.org/wp-content/upload...CFR-Approved-2015-12-14-Posting-Copy.pdf

You're right! But they're optional....

Ah. I guess i just happened to see some that did have twists. Learn something every day

Dan,

What I'm wondering is why some would question whether a 250-grain, flat-based spitzer won't stabilize in a 1-16 twist. Remington's standard twist in the .350 Magnum was 1-16, and one of their original factory loads featured the 250 Pointed Soft-Point Corelokt. For some reason they changed that to a round-nose when they introduced the .35 Whelen as a factory load, but they stuck to a 1-16 twist, and a lot of handloaders used 250 spitzers without problems.

Maybe it has to do with the persistent belief that muzzle velocity has a vast effect on bullet stability, to the point where a certain bullet will shoot inaccurately at a certain velocity, or even tumble, yet will stabilize when pushed 100 fps faster. While extra velocity does have a slight effect, it's far less than the effect of temperature or altitude.

Another item I wanted to mention was that the Berger program works best with boattail spitzers, especially those with very high BC's. It isn't as accurate with flat-base spitzers, though quite often they stabilize easier, due to more drag on the flat base. The Berger program also doesn't account for the fact that the length of plastic tips doesn't "count" nearly as much in overall bullet length, due to the very light weight of the tips. Which is why some varmint shooters believe the 40-grain Hornady V-Max is too long for the .204 Ruger's standard 1-12 twist--which is actually plenty. The JBM twist program has a place to note the length of a plastic tip, so is more accurate with those bullets.

John, I have no idea where the “wisdom” came from, but several fellas were perfectly convinced my .358 wouldn’t shoot the 250’s. That’s all I ever shot and the gun was consistently sub MOA at 100 yds, even with (gasp!) factory ammo.

Anyhoo, I understood that SAAMI specs compliance are voluntary. Helps keep me on my toes.