I have NEVER been able to come up with repeatable numbers when checking the twist with a tight patch. I have been cogitating on this idea for a long time and finally decided to give it a try. I wanted to verify the twist on my factory sporter Remington 700 223 bbl. The black stuff sticking out the front of the 22 RF bullet is flat carbon fiber strip about 1/8" wide. I used a razor saw to cut a slot in the front of the bullet and crimped the CF strip in place. Then I used a CF rod to push the slug just into the bore from the chamber end. I put a strip of tape on the CF strip right at the muzzle, noted the orientation of the strip and then pushed the slug down the bore until I got one full revolution. Then measure from the muzzle to the tape and voila, 11.750".
Later I expanded another slug and used it to check a couple of 6mm bbls but it was harder to get the now blunt nosed slug started in the rifling and while I was able to make it work I would recommend sourcing proper sized lead bullets to suit whatever bore you want to measure. Both of the 6mm bbls measured just under 14".
Later I expanded another slug and used it to check a couple of 6mm bbls but it was harder to get the now blunt nosed slug started in the rifling and while I was able to make it work I would recommend sourcing proper sized lead bullets to suit whatever bore you want to measure. Both of the 6mm bbls measured just under 14".
I mean, what's the difference (on paper) between say, 1:11.750" and 1:12? I'm genuinely interested because I don't think I've ever bothered to check the twist rate on a barrel, beyond an initial "yep, that's 1:9-ish alright".
