bob4432 Wrote:Title says it all.
Please explain if there is a difference.
Thanks,
Bob
Bob,
Depending on the quality of gun, ammunition, rest, weather conditions, range, and your ability to shoot you probably won't notice the difference. Or more importantly, not be able to tell whether the twist is the reason for the group size.
6.5's come in a range from 1:7 to 1:9 with the majority of drop-ins in the middle 1:8. I have shot a 1:7.5 Pac Nor 'Super Match' in 6.5x47 shooting 130gn bullets and got larger groups than 1:8 Kriegers, but am tempted to think it's the barrel quality rather than the twist. I've only had one faster than normal twist barrel in 6.5mm so we should not be generalizing to your situation. In 223 F Class I have used a slightly faster twist 1:7", than the normal 1:8", to stabilize the heaviest 90gn Berger bullets, but again results on target were a big yawn.
In 6.5mm Shilen recommends 1:7"-1:8" for bullets 130gn and heavier, and for lighter than 130gn, 1:8"-1:9".
In 300Blackout, in the early days the standard was 1:8" but is now 1:7" across the industry, to stabilize the heaviest 200-220gn subsonics.
The point being, faster twists to stabilize heavier bullets and slower twists if exclusively shooting lighter bullets is the general principle, but there can be a cost to spinning bullets too fast. Over-stabilized rounds resist pointing to the target after apogee, so for long range shots this means wider groups. Plus any imperfections in the bullet get magnified the faster you spin it, again larger groups. In extreme cases overspinning a bullet has it coming apart somewhere downrange before the target. LeHigh now includes advice on spin RPM for their 30cal Blackout type bullets after they were coming apart in shooters' suppressors, damaging them.
To be fair, the difference you are considering is slight and if anything favors heavier bullets. Up to you but I doubt you'll notice any difference (all other things being equal).