My old Les Baer, with the 1 1/2” @ 50 yard group guarantee has a Kart barrel. I’m guessing it has 10k through it and it’s still a b#*#h to take apart. Can barely turn the bushing even with a steel wrench, and then have to use a brass punch to tap it out. Once the bushing is out, Getting the barrel out is almost as tough. I also have a Wilson that went to Rock River Arms, a long time ago and they fitted everything just as tight as the Baer and came back with an 1 1/2” group guarantee at 50 yards. Neither pistol has ever missed a beat. I have 2 full custom “open” guns that have hard fit barrels in them that are a little more accurate, but not by much. One open gun originally was a 38 Supercomp that I also had a 9mm barrel fitted, and the other is 9mm.
In MY pistols, Zero or Nosler jhps are the most accurate, but with the availability issues I’ve been using a lot of Precision Delta jhps and even though they aren’t as pretty, they’re very accurate out of MY pistols.
Your mileage may vary.
Good luck with your project.
let us know how it shoots.