I had one with the micro groove rifling. No matter what I tried, I could not get consistent accuracy at 100 yards. I had these great looking LBT 300 grain, cast, gas checked bullets that I could not hit a barn wall with. Probably due to the slow twist, and the micro groove riflng. Then again, I couldn't get any better accuracy with jacketed 240 and 265 bullets. As another poster put it, "fun to shoot", but not reliably accurate. I so wanted to connect on a deer with those cast 300 grain bullets, but it never happened. I ended up loading them in my 444, and dropped a number of deer with that. Mind you, the accuracy was not anything to write home about with the 444 either.