vtjonny5 Posted January 18, 2019 Report Share Posted January 18, 2019 Hello from Vermont! I am an online forum virgin, so please be gentle. My AR knowledge is pretty basic, but my overall firearms knowledge is definitely above average (average person, not average gun enthusiast). I purchased my first AR a few years ago, (now i have 7, dont tell my wife) and had an AR 10 built for me by a local custom shop a few months ago. This shop machines their own lowers (or has someone machine them). My gun has a match grade stainless fluted barrel. When I first got the gun, I had difficulty extracting live rounds out of it. It was all but impossible to pull the charging handle back. I brought the gun back and they put on a new barrel (my first barrel was blued). This seems to have fixed that issue. Every round I've fired through it (from both barrels, the new one and the old one), the primers on the empty cases are cratered...............badly. So badly, in fact, that when you stand one on it's end (on a table, for instance) it tips noticeably to one side. I've tried a number of different factory rounds in this gun, all had cratered primers (Hornady Superformance, Federal Fusion, Fort Scott, Remington Core-lokt, and Winchester Deer Season XP). My reloading experience is telling me there is a pressure issue, but nearly all of my gun experience is with bolt actions, not semi-automatic, and certainly not AR's. So, im not 100% confident in that assumption. I want to eventually reload for this gun. I did measure a fire formed case with a hornady lock-n-load headspace gauge. The Fort Scott ammo measured .010 shorter than my fire formed brass. The Hornady was .008 shorter , and the Federal was .005 shorter (and also grouped the best). I didnt get to measure the Remington or Winchester, that was ammo a friend let me try when we were at the range. Just shot one of each to see if it cratered (it did). Any advice on which direction to go from here would be great. Thanks. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted January 18, 2019 Report Share Posted January 18, 2019 46 minutes ago, vtjonny5 said: When I first got the gun, I had difficulty extracting live rounds out of it. It was all but impossible to pull the charging handle back. This,by itself, is a classic sign of over-pressure in a gas gun. But, hold on... You followed with this info: "Every round I've fired through it (from both barrels, the new one and the old one), the primers on the empty cases are cratered...............badly. So badly, in fact, that when you stand one on it's end (on a table, for instance) it tips noticeably to one side. I've tried a number of different factory rounds in this gun, all had cratered primers (Hornady Superformance, Federal Fusion, Fort Scott, Remington Core-lokt, and Winchester Deer Season XP). My reloading experience is telling me there is a pressure issue, but nearly all of my gun experience is with bolt actions, not semi-automatic, and certainly not AR's." Those aren't over-pressured rounds, as factory ammo - no way all that ammo you picked up was over-pressured... Over sized firing pin hole in the face of the bolt. Diameter of the firing pin tip is pretty much "standardized," as much as they is not a standard on the Big AR... DPMS was notorious on that specific issue on the earlier G II, with an oversized firing pin hole... Really need to know part specifics on what you built, before anyone here can comment on all the possibilities. List it out... Quote Link to comment Share on other sites More sharing options...
vtjonny5 Posted January 18, 2019 Author Report Share Posted January 18, 2019 Thanks for the reply, I'll put a specific parts list together and get it on here (I'll have to ask the builder, I'm not 100% sure). My comment about being unable to pull the charging handle back was with live rounds, not spent cases. If you put a loaded mag in, cycled the charging handle (to put a live round in the chamber), then dumped the magazine (without firing a shot), it was extremely difficult to get the LIVE round out of the gun. Not sure what that was caused buy, but I know it wasn't chamber pressure because the gun wasn't fired. When they put the new barrel on, that problem went away, but still cratered primers. Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted January 18, 2019 Report Share Posted January 18, 2019 Welcome from Iowa, via Missouri! I have some cratering on my Matrix build with a D Wilson BCG, not been an issue to this point. Quote Link to comment Share on other sites More sharing options...
edgecrusher Posted January 18, 2019 Report Share Posted January 18, 2019 Hand cycling a new large frame will be difficult if: it still needs breaking in or is under lubricated. These guns sometimes need 200 rds plus to break in and may need to be dripping wet. Quote Link to comment Share on other sites More sharing options...
edgecrusher Posted January 18, 2019 Report Share Posted January 18, 2019 As for your other issue we will wait for the list. Welcome and enjoy some threads while you’re here Quote Link to comment Share on other sites More sharing options...
shepp Posted January 19, 2019 Report Share Posted January 19, 2019 Welcome from Wisconsin Quote Link to comment Share on other sites More sharing options...
Rsquared Posted January 19, 2019 Report Share Posted January 19, 2019 I'm with Tom (98) on this one. Sounds like an oversized firing pin hole in the bolt. Oh, and welcome aboard. Quote Link to comment Share on other sites More sharing options...
unforgiven Posted January 25, 2019 Report Share Posted January 25, 2019 Welcome from Indiana brother Quote Link to comment Share on other sites More sharing options...
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