I had an issue with x-caliber. Got a 1-9 twist 24 inch 300 PRC barrel from them. Wanted to make sure I did everything as tight and up to their tolerances I could. Per their recommendation I used a barrel nut from PTG to use with the setup on a Stiller predator action. Dave at PTG actually put the barrel on for me. Well went to breaking the barrel the right way with their recommendations. Wasn't great groups out of the gate with Hornady factory 225 and 212 ammo, maybe 1-1.5 MOA. Was a very hard barrel to get clean and took a few extra processes the first few times. after about 15-20 shots of slow break in it was grouping well under MOA. Did some long range work out to 600 and couldn't hit the target(12inch steel). Did another round of cleaning(after 3 shots it was crazy dirty). While cleaning I noticed the barrel nut was loose. A trip to the gunsmith to tighten it up and check things over. All looked good and I wrote it off. Got to shooting again and it started off good(around 1/2 MOA). Was at around 30-40 rounds now. After a handful of rounds I again couldn't hit my targets and it was shooting all over the place. (Side note is it was being shot off and on Omega 300 suppressor and SWAG muzzle brake(not the reason for misses)). Checked the nut again and it was loose. Well now I'm irritated and have lost all confidence in this rig. Called x-caliber and sent it in to get checked per their recommendation. Apparently in millions of dollars of sales they have never had an issue or ever heard of a nut coming loose. After they checked it they are saying it was the barrel nut and the fact it is Teflon coated. well I can by that I guess. I have No confidence in their barrel anymore even though they ended up giving me a used barrel nut they had To try. I was Not happy how they treated the situation and maybe I am in the wrong But I thought they would take care of the issue since I did everything per their recommendation and no longer wanted this barrel. I was hoping that they would refund my money for the barrel. Well they couldn't do that as it was a great barrel that any of them Would be happy to shoot. I guess I was asking too much of a company who has never had any barrel issues before. So if anyone is looking for a great barrel that's well broken in(their words) check out the classifieds. Make me an offer, and see if their recommendation was spot on because I am not continuing down that road. Just not sure a remage setup on a magnum is a good idea after this. Have a criterion in 6mm CM and it's great. For my magnums I will stick to a shouldered barrel from now on though. Merry Christmas