Bartlein gain twist barrel

I know it is not a rifle but for what it's worth S&W uses a gain twist on there 460 XVR revolvers. The twist starts off at 1 turn in 100 inches and ends at 1 turn in 20 inches. I think they very the depth too but not sure about that. I have been considering a gain twist for a .264 Win Mag build I would like to set up for 150 and 156 weight bullets. Just not sure. I was worried a 1-7 might damage bullets.
I recently had a 264 win built with a bartlein 32" 8 - 7 twist built specifically to shoot 150g + projectiles. I have only had a chance to fire a total of 62 rounds with 160g Matrix bullets.
To this point it has surprised me on a couple of levels. Primarily, the velocity it is able to safely attain. I'm using Norma 217 and I safely shoot the same powder charge as I used with the 143 ELDX. Secondarily, how easy it has been to tune. I have three other 264 win rifles and this one has literally shot every load combination I've tried 3/4 MOA or better. I've only had it out to 300 yards so far. Next trip to my buddies private range I'll start at 500 yards and be working out further to hopefully 1,300 yards.
 
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