Twist rate effects on terminal ballistics

[solarshooter]

Same loads as the old rifle, just had to adjust p.o.i. after new barrel. Same length, as far as hitting stuff, i've hit dozens of pigs (usually I try for neck, but clients and friends go for the shoulder) and the 4 since new barrel are catastrophically different. This new barrel might be faster by a little but not so much as to see these results.

AB says the 150SST at 2880 out of a 1:12 twist has a stability factor of 0.91. This is very low, and at the least is causing a big decrease in BC and impacts that are not point-on, if not complete tumbling of the bullet. Additionally, an old barrel with worn lands can cause tearing on the surface of the jacket and inconsistent engraving in general, further compromising bullet flight and possibly terminal performance. I'm guessing this might be more the cause of your observed differences in performance.

 

[180ls1]

yes, at that velocity, my 16" 6.5 Creedmoor with the 1-7 twist MV is 2494. which puts it at 256,525 RPM. Not really sure what you are getting at, my statement was the difference in my rifle and an advertised 6.5 PRC. Using bonded, or solid bullets at faster twist rates is necessary. That 10,903 rpm difference @ 2600fps isn't going to make much of a difference.

Interesting you say this.

My 6.5 PRC is a 7 twist and has blown me away how devastating it is on game. I run 124 hammers in it @ 3400.

 

[Elvis442000]

261,800 rpm vs 172,800 rpm.

It makes sense to me that the forces on the bullet would be drastically different even if velocity is the same.

Of course, rifling could be cutting the jacket differently making the jacket more fragile. Or, could be a combination of both.

Good thought. That old barrel had about a bazillion rounds through it.