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Posted: 2/23/2008 9:09:46 PM EDT
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I've been building AR's for a few years now, but I've got some new issues I've yet to encounter and I need some help/advice . I've assembled an upper, 16" SS barrel, carbine length gas system, YHM specter gas block, YHM free float tube, A3 upper. I've noticed the brass is ejecting at about 2:00-3:00 out of the ejection port, and the recoil is more pronounced than in my other carbines. I'm afraid the system is getting over pressurized. I've run powder puff handloads, 24.3gr of H335 behind an SS109, all the way to some M193 spec'd Guat' 55gr ammo. The brass piles up at 2:00 or so and the recoil is way more pronounced than normal when its running fine (which leads me to issue #2). Also, the carrier/bolt doesn't always chamber a round fully from a fresh mag. The bolt only closes about 90% and its a major PITA to extract via the charging handle. I can just feel it stop before going fully into battery on a fresh mag after hitting the bolt release button. Help please 
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Will the bolt lock back on the bolt catch if you fire just a single round loaded/charged from a mag through the rifle (short stroking test)? Is the spent case deflecting off the deflector of of the ejection port, then being bounced forward, or is the spent case just being ejected forward without touching the deflector? Start with the short stroking test, and we can go from there. |
Ok, I answered the questions above. My biggest issue is the bolt not going into battery. I thought maybe my buffer springs were needing a replacement, so I swapped lowers and used an A2 buttstock/buffer assembly off of one of my varmint rigs. Same deal happened, failure to go fully into battery, no joy with using the forward assist either. I've tried 2 different bolts and 2 different carriers. Still F'ed up operation. 
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I'm not an expert, but supposedly there are two issues with ejection patterns. Gas and bolt speed being first and most important, but the extractor is second and more likely an issue when a chambering problem is associated with the ejection pattern. If the extractor is overly tight it cannot climb over the "rim" to capture the round at the last possible portion of chambering. The fact that you have difficulty even with the forward assist would seem to back that up. If you have a dounut under the extractor and the spring, try just removing the "O" ring. Could be that simple! Good luck and good shooting. Two outstanding links: Armalite Armalite tech notes |
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Sounds like you have two problems, so lets attack them seperatly. On the fail to go into battery, where is the tip of the bullet when the B/C locks up. Is this a problem with low feeds (marks under the barrel extension on the upper) or is this a problem with the hammer just catching the FP collar. As for if the bolt is locking open on the last round, and you are getting beat up a bit by the buffer off the back of the receiver extension, then the action/cycle is not being controlled correctly. This could be from a recoil spring being too weak, or just the gas port over sized and you would need to increase the buffer mass to compensate for it. With the information given, it does sound like the instead of the buffer stalling at the rear of cycle, it's just getting sling shotted back forward instead. |
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