Standard twist rate for a 40XC is 1:12". Such barrels will shoot 190 Sierras reasonably well, friends used to use modified Remington Varmint Synthetics (same twist in factory barrels) with 'em to shoot Palma. Have shot 185 Berger VLDs from a VS barrel at 1000 yards, no complaints about accuracy (IIRC, 7 shot group of ~8" @ 1000.) Anything longer than a 190 Sierra will probably result in bullet patterns at 100 yards (with more than a few elongated holes).The only drawback on that gun for f/tr is too slow of a twist to shoot the mainstream bullets.
Bullet length.
Yea we gotta make sure you didnt buy that single shot rifle in haste. You know how dangerous they can be.
Just looking at the wear on the forearm from a shooting glove, I'd say it has seen some shooting. Interesting to see what's left in the barrel. Those are excellent barrels, by the way. My Dad had the same rifle but in single shot form. Still has it, I think, but with it's third or fourth barrel. Regards, Bill
If I were you the first thing to do is take a look at the bore....I've competed in NRA High Power for close to 40 years, those barrels do wear out....and when there is wear on the wood finish usually the barrel is toast.
I'd never buy a used 40X at these inflated online prices, which is why my F-Class FTR and Open rifles are built off Rem. 700 actions.