Can't help you with the bore but I have a R15 204 22" and love it. I doubt they were doing mag dumps with the 204 so unless they used it shooting a lot of prairie dogs I would think it would be fine. I'm sure a good cleaning might be in store. You'll just have to see how it shoots for starters. Mine will not shoot 40gr bullets and so far I haven't reloaded for it. Mine prefers Remington 32gr Accutips and they work great on coyotes. I only use mine for coyote hunting and bought it new when they came out 10 - 12 years ago and it doesn't get cleaned very often. Also mine will not feed Winchester 34gr hp reliably, it was pushing the bullets back into the case. I use 20 round Brownells aluminum mags. Colt mags will work too, I haven't tried any others.