Re: AR15 1:10 best reload
The twist rate may not have anyting to do with this problem. It may be that one type bullet is better seated close to the lands than the other. You can get terrible performance with long bullet jump and a loose chamber neck from blowby or with bullets where some jam into the lands and other are pushed back into the case on chambering. A 10" twist should be ok for both 55 and 69 grain bullets for normal air densities.