All of the load books that i have develop their data for a 1:14 twist. I have a 1:12 twist. How much should I back off of the published data?

The pressure difference between a 1:14" and a 1:12" twist is of no consequence. Use your published data as is.

quote:

Originally posted by Gerard:
The pressure difference between a 1:14" and a 1:12" twist is of no consequence. Use your published data as is.

The only problem here is that you might blow up some bullets due to too much RPMs but the loading data for most all loads will not be affected.

With a 1:12 twist, you'd be best served with 55 grain bullets. The Swift is easily capable of "blowing up" 45 grain bullets when operated at full-throttle, and that's with the standard 1:14 twist. Some of the lightly constructed 50's also have a reputation for frangibility, so they wouldn't necessarily be a first choice either. On the other hand I don't think the 1:12" will stabilize a 69 grain bullet either. Having said that, I think the 55 grain "Ballistic Tip" would do you proud.

The solution for me has been 40gr monos in the 1:14 Swift at 4400fps. The rifle has since been rechambered to a wildcat that allows 4700fps with the 40gr HV bullet. No worries about bullets blowing up in the air and great performance on game that would traditionally be regarded as too big for the bullet/caliber.
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