30 Cal, 1:9 Twist

[dcali]

To put some numbers behind it, I have tested this in a round about way by using the same bullet with differing weights in the cores. The shorter cores are predicted to be more accurate, and they are, by roughly what the math says they will be. I know that's not exactly what we're talking about, but theoretically it may as well be - it's a matter of twist and bullet geometry. Long story short, you can expect *very rouhgly* a 20-30% increase in group size goigng from a 12 to a 9. That depends on a lot, so mileage may vary, but I that's about the size of the change we're talking about. For hunting, or shooting steel targets at long range, it really isn't a big deal. But it turns a good F class rifle into a mediocre one, and a good benchrest gun into a poor one.

 

[DanW]

I recently went back to a 12 twist to shoot the lighter bullets. The 9 twist I had liked the heavier bullets, 190s / 200s, but the groups got bigger as the bullets got lighter it seemed. So far Im pleased with going back to a 4 groove stainless 12 twist.

 

[willbas]

I just got a 9 for my F-TR rifle and I am shooting the Sierra 200's so far so good. I just have to find my final seating depth this weekend.