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GUNS Magazine March 2010 - Page 10
UPONARS • GLEN ZEDIKER • TROUBLESHOOTING Bringing back the bang. f an AR-15 won’t work, well, it has to work. Here are a few places I to look and a few things to try if yours goes on the fritz. The first question is always, “What changed?” But before then we have to determine, or at least I do, whether we’re talking about: a “fresh” rifle going through its shakedown period or a (previously) trusted gun that’s suddenly decided to stop running. If it’s the first, a longer list of possibilities includes original parts’ condition and installation quality. In other words, there’s a long list of suspicious items and it’s a chore checking it. agasmanifoldshouldbeseatedfullyflushand securelyagainstthebarrel. Here’sthetoolthatdoesit,aMOaCKSPlain. it’ssimpletouse.Thetoolusesthekeyscrews toindexitselfandthenhardenedscrewsthread intoproducethestaking.Here’swhatthe carrierlookslikeafterstaking. TheMarkBrownCarrierScraperfromBrownells isamusthave.afewturnseachcleaningwill preventcarbonbuildupfromruiningyourfun. Thevolumeofgrungeemergingfromtheuseof thistoolonadirtycarrierwillamaze. 10 If a once fine working AR-15 starts having problems, and these problems are exclusively failures to cycle correctly (fire, eject, reload), the first question is, what changed? If different ammo was used, it ought to be clear to check it with previously used ammo. Reasons range from clear to cloudy, but not all loads function the same in all rifles. If you’re a handloader, double-check your current cartridge dimensions to make sure nothing changed in your dies, and certainly look again at the charge settings, etc. This is a reason to keep loaded samples handy. If it’s a failure to eject a spent case, weakened gas flow or grime come first to mind. Or a broken extractor spring. Or a broken ejector spring. These two springs, by the way, usually break rather than weaken. Most often a heretofore reliable rifle starts short-stroking. A “short stroke” happens when the carrier doesn’t get far enough to the rear to pick up a cartridge from the magazine to chamber the round, and the bolt also won’t lock back because the bolt stop can’t engage. The cause for this is either not enough “oomph” from the gas system (a leak) or too much friction or resistance in operation (grit and grime). One of the most overlooked and also more common causes for abated gas action is a loose bolt carrier key. There will be your leak. If it’s installed correctly it should not come loose. Should not. Installed incorrectly, it probably will come loose, and I’ve seen many incorrectly installed. The key is held fast by two screws. These screws have knurled heads. Most Loctite“blue”onthesetscrewsisagood ideabutGlendoesn’tliketheriskofgluing themanifoldtothebarrel.Glueandgasports don’tagree. specs I’ve seen call for 30 to 40 inchpounds of torque, and I say that’s not enough. They need to be tighter than that. Most of the better builders I know don’t use a torque wrench for this op. Just tight. Now, the trick is these screws also need to be staked in place. Here’s the stem for the problem. There seems to be an increasingly growing number of carrier key screws installed using threadlocker (the “red” high-strength) in lieu of staking. I’ve been seeing this from major makers as well as carrier assembly suppliers. Glue is a fine extra if someone wants to use it but if the keys aren’t staked they are not going to stay put. Staking carrier key screws is best done using a specialty tool but can be, for effect, done with a prick punch and hammer. It’s not always going to be a pretty job using hand tools, but as long as some metal is displaced inward from the key to the screws to secure the screw heads from rotating, it will be functional (that’s why the screw heads are knurled, by the way). The series of MOACKS specialty tools available pretty much mistake- WWW.GUNSMAGAZINE.COM • MARCH 2010