I have a Cooper in the 6.5 PRC that someone wants more than I do. I am going to regret this, as it will shoot 124 HH in the .2's. I do not want to be without a 6.5 PRC and I was looking at the Proof Research Tundra, and G. A. Precision rifles. Both of those firms are twisting their barrels at 1:7.5 twist vice Coopers 1:8 twist. What is this giving me that the 1 in 8 twist doesn't?

I know this should go down in the reloader forum, but I figure most reading here are reloaders and can tell me if the 1:7/5 will stabilize the 124 Hammer Hunter bullet.

It’s a faster twist than your 8 twist. It will stabilize anything the 8 does and likely a bit more.

I wouldn’t worry. If they shoot in the 8, they’ll work just as well in the 7.5. Maybe better terminally as well.

Sierra recommended 7.5" for their 156gr Matchking...you like copper projectiles, so when they make a copper heavier than 130gr, you might want 7.5" twist.

There's also a considerable difference when shooting at higher elevations. A general rule is that every 5000 feet in altitude requires 1" less twist for bullets to stabilize.

20+ years ago I had a 6.5-06 with a 1-9 twist, because a barrel company offered to build me one--and that was the fastest 6.5 twist they offered at the time. Generally I hunt locally at around 6000 feet above sea level, and the rifle grouped 140-grain Berger VLDs into 3" for 3-shot groups at 600 yards. Obviously they stabilized very well.

The Berger bullets stabilization formula (and some others) can provide a good comparison between various altitudes, and other programs work well too.