Sadly, I didn’t know about this forum before I bought my Rock River, so I ended up with a 1:9 twist. I realize that 70+ grain bullets are getting heavy for a 1:9 twist, but I was wondering if anybody has tried them with Rock River 1:9 barrel? I suppose the best thing is just try them.
Yes. Some have been better than others. 1/9 is suboptimal for shooting the heavies, but it’s not incapable. At short to intermediate ranges, you likely won’t notice.
Some 1/9 barrels do okay with them, most do not. If you’re going to try them, I recommend shooting at 100 and 200 yards. Variations in accuracy and key holing are likely to show up there. You’re most likely not going to notice anything at 25 - 50 yards. Otherwise, there are plenty of good 64-69 gr loads available…
I would just shoot bullets under 70 grains and not worry about.
It’s not always the weight of the projectile which requires a fast twist faster than 1x9. It’s the length of the projectile. A M856 tracers 64gr projectile is actually longer than a MK262 77gr projectile. This is why the military used the the 1x7 twist first in the M249 and later in the M16A2, A3, A4 and the M4. 1x7 was required to stabilize the M856 64gr projectile.
It won’t hurt anything if you try a box through your gun but you should try it at 100-200yds to see if it’s keyholing at distance. I’ve seen quite a few 1x9 twist barrels which stabilize rounds up to 75gr.