Surely ... this is not news to FAXON ... but I was blindsided. A very disappointing experience ... x2. Life. If only in their details/descriptions they included this information (and the required use of an adjustable gas block), I would/could have taken it into account while making my component/purchasing decisions ... and I would be making initial sights/optics decisions today. I reeeeeeeally like these 2 Uppers that I have assembled (as well as the GreenMtn Upper, mentioned in the email text below) and look forward to having this situation resolved. I will update after FAXON responds. =======[ email that I sent to FAXON last night ]======= @SUBJ: Overgassed? Issues with 2 of your Gunner barrels Hello. Recently I was bitten by the AR Building Bug (directly connected to deciding that it was time to enter the Free Floating Handguard World), something that I have successfully avoided for over a decade (my last two AR Builds were in 2004). I ordered a new-mfr 1:12 M16-Profile pencil barrel (for some lighter-weight-bullet action) from Green Mountain, which I received a couple of weeks ago, and decided upon two 1:8 5.56 Faxon Gunner barrels. You have no idea how much I have been looking forward to getting my two Faxon 5.56 Gunner barrels, a 20" from AR15Discounts and a 16" from Brownells. As with the GreenMtn barreled-Upper a week ago, after checking headspace on both Faxon-barreled Uppers I attached them to Lowers (20" with an A2 rifle stock & 16" with an M4-style collapsible) and headed into the backyard for a quick testfire on each. I only had 7 rounds left in the open box of the SouthAfrican M193 that I use so I fired 4 in the 20" and 3 in the 16" ... collected & segregated the cases and return to the house to inspect them. The 20" cases looked bad and the 16" cases looked HORRIBLE. The first thing that came to mind was unpolished chambers but I quickly discarded that thought as I thought it thru. It appears obvious to me that with both rifles the bolt unlocked before the pressure dropped to release the cases from the chamber walls, creating what are apparently drag marks on the cases. Is this what "overgassing" does? Causes an early unlock scenario and the extractor tries to DRAG the cases out? Here are 2 pics, this first of the Faxon chamber markings on my barrels: This 2nd pic shows 3 sets of fired cases. On the left are the 5 that I (test)fired in my GreenMtn rifle, in the middle, the 4 that I testfired in the 20" Faxon rifle and on the right, the 3 that I testfired in my 16" Faxon carbine. BTW, it does not show in the pic but the "drag marks" are also on the case shoulders of the Faxon-fired cases. Looking at those carbine cases (3 on the right) it crossed my mind that it was surprising to me that they managed to be extracted. Close inspection of the rims testified to the additional force exerted. I carefully cleaned the rifles and went back out to test fire again. The cases produced by the 20" were more of the same. The 16" only managed a single shot and then failed to extract, ripping off a chunk of rim with the effort. After thinking about it a bit, I cleaned the 16" again and mounted it on the A2 Lower to see if the heavier rifle buffer would make any difference. Nope. All I managed to do was get another FTEx with another chunk of rim ripped off (join me in prayers for the health of that extractor ). --------------------------------------------- So ... it appears that I have invested over $300 in my two Faxon barrels (and hundreds of dollars on components to build up rifles around those specific barrels) that, as it turns out, are overgassed (one severely, so) and, therefore, require the additional purchase and installation specialty adjustable gas blocks in order to be able to even use them. <sigh> Does that sound like a fair summary? S'funny ... I was greatly intrigued by those Superlative(?) adjustable gas blocks that you have on your website. They appealed the my Geek Gene. But the thought of spending $180 on adjustable gas blocks for ~$300 worth of barrels, especially when I do not use them in a way the needs the gas blocks to be adjustable was a No Go. Anyway ... my two new Faxon-barreled Uppers are safely tucked away in my north gunsafe until I can sort out this mess. I would like to hear your thoughts and/or advice on my situation and the accuracy (or inaccuracy) of my assessment of what is happening with these barrels. Thank you! I look forward to hearing from you!