I just got a Hart barrel in I purchased lightly used with around 600 claimed rounds through it. I cleaned it and scoped it. It is a thing of beauty inside. I can hardly make out any tool marks, but I am still learning how to use this bore scope. It is a 5 groove left hand twist barrel 1 in 10'' twist, nitrited, 2x cryo treated. I cant wait to twist it on to try it out. I will follow up once I try it out.