Lothar Walther barrels ......
I use 2 Walther barrels and think they're excellent. One is their 10/22 barrel chambered for .22Mag, and it shoots very well with several different brands. The other is a 22-250AI and that barrel is just amazing. I did no break-in...the first 35 rounds were load work up. There was NO copper in the bore. The next 45 rounds were shooting prairie dogs, and again there was NO copper. Even after 100 rounds, Sweet's will produce only the slightest trace of blue. I clean the gun mostly with Butch's or Montana Extreme and wet patches, it sees the brush very little if at all. This is fireforming with waxed 50's at 4110fps. The chamber has a .255" neck. My other heavy barrel 22-250AI has a Hart barrel with .250" neck - with 3" more length and FORMED cases, it gets 130fps more velocity. Both guns shoot about the same, in the .2"s - .3"s...the during load workup the Walther actually shot some groups in the .1"s, both fireforming and with formed cases. Their stainless is different stuff and not really any harder, but a lot tougher. Because of that, some people have problems chambering them. Talk to Walther or Dave Kiff at Pacific Precision and either of them can help you. I don't baby that gun and the barrel has probably 1,200 rounds through it. It's also been real hot a bunch of times, yet the throat has grown by only about .010"-.012". I have barrels from 12-14 different manufacturers and none are more accurate than the Walther. It's my favorite.