I am confused. The announcement of the new Ruger Precision Rifle has added to my confusion. Admittedly, I am not a ballistics expert nor am I a physicist. Also, my understanding of ballistics and physics pales in comparison to many members of this forum. So, I humbly seek answers from you. I am in no way trying to put down this new rifle. I would really like to have one. I merely do not understand some things.
The Ruger Precision Rifle is billed as a "long range precision rifle". In at least one of the reviews that I have read on this rifle, it was stated that the use of a fast twist for caliber barrel was done in order to stabilize the heavy projectiles used for long range shooting. All of which I understand. What confounds me is the use of the 20 inch barrel for the 308 Winchester with a fast twist, intended to facilitate long range shooting. An article online, www.tacticaloperations.com/SWATbarrel/, states that when using a 168 grain load in a 308 Winchester, a complete powder burn can be achieved in a 20 inch barrel. Am I correct in assuming that if using a heavier projectile, a longer barrel would be needed to achieve a complete powder burn? In looking at Berger's website, the fastest twist needed for any 168 grain 308 caliber bullet is 1:12. The Berger website shows that only 215+grain 308 caliber bullets need a 1:10 twist. If I remember correctly, the 175 grain 308 caliber bullet is supposed to be ballistically superior to the 168 grain bullets at 1000 yards. Which I assume was why the 175 grain SMK was adopted for the M118LR round by the US military. So, why would a rifle intended for long range precision be setup with a fast twist barrel that is too short to facilitate a complete powder burn when using heavy bullets? Also, if long range precision is the goal, wouldn’t the added velocity from a 24 or 26 inch barrel shooting 175+grain bullets be desired?
I would have expected Ruger to hang a 24 or 26 inch barrel with a 1:12 or 1:11 twist on the 308 Winchester version of this rifle. Am I wrong in thinking that the longer barrel with a slightly slower twist would still handle the heavy bullets, allow a complete powder burn, and provide the additional velocity needed for long range precision? Or if this rifle was built around the 168 grain bullets, why wasn’t a slower twist used in the 20 inch barrel and the rifle stated as being built around that class bullet?