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Posted: 1/30/2013 9:56:54 AM EDT
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Hey all,
I'm having a few issues with a gun I have been building as a gift for my dad, and am hoping you guys can help me pinpoint the problem. Yesterday I test fired by putting 20 rounds through it, and noticed some issues with the ejecting brass - it was ejecting to the 1 o'clock position rather than 5ish. You can tell from the picture that it is hitting just in front of the deflector, which is causing it to bounce forward rather than deflect back. 
When I got home I attempted to recreate the problem by chambering an empty cartridge to see how it interacted with the ejector. However, chambering the cartridge caused the bolt to lock up solid. I mortared it free, pulled the bolt, and found it to be in this condition. 
The wear seems excessive considering the carrier and bolt have only seen 20 rounds. Also, along with the brass markings on the bolt face, there were a lot of shavings I wiped off the carrier as well. I am assuming the issue is with the ejector, but I really just don't know. Everything with it looks normal, and I already tried it with a new ejector spring, but the results were the same. I did inspect the brass, but in all my wisdom I did not bring them home with me or take a picture. Pretty big fail... I can tell you, however, that there is a long scrape running about half the length of the cartridge, as well as a dent about midway (I assume that is where it is impacting the receiver when ejecting). Any ideas on what could be causing all this? Thanks, Sam |
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The brass deflector just doing it's job. The brass is not making it to the deflector. It is hitting off the front edge of it and bouncing forward. Quoted:
Only problem I see is the BCG is way under lubed. If it is ejecting you have no problem just over thinking it. If you want it to change work with changing the buffer weight. I wiped down the BCG for pictures. I run it dripping wet. Also, it is an A2 buffer, I don't think I have much option in weight. My main concern is not really where the shells are ending up, but I think it is a symptom of a more serious problem. I can not think of a good reason why the bolt carrier would completely lock up when chambering an empty cartridge. |
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The extractor is nice and sharp, it will leave brass shavings on the bolt face. The casings get beat up by running in the rifle. Normal.
Brass striking the receiver as you show is common as well. The brass is being held firmly by the extractor and the ejector is not pushing the brass out of the ejection port soon enough. As parts wear in together, they will reach a point where the ejector is throwing the brass out of the port sooner because the extractor is not as tight. Don't sweat it. The empty casing has been fired and has expanded in size to the chamber. It is now larger than an unfired round and it is normal for it to be hard to extract when manually run through the rifle. Your rifle can change it's ejection path by changes in ammo, lubrication, temperature, parts wear, etc... As long as the brass is thrown clear and it runs fine, no worries. |
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Your carrier might be moving a bit fast. May think about going up a level in buffer weight. I supposed I ought to elaborate a bit more. I am running a 16" carbine length barrel, with an A2 stock/buffer. I have been wondering about this setup as it is the same buffer as a rifle length gas system, but way more gas. It makes perfect sense that it is cycling too fast, but from everything I have read the setup should run fine. The setup is very new to me, I have never built a fixed stock AR before. But I really am not seeing any heavy buffer alternatives for it... Thanks again for all the help, Sam |
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The empty casing has been fired and has expanded in size to the chamber. It is now larger than an unfired round and it is normal for it to be hard to extract when manually run through the rifle. This
Might also be a little over gassed due to 1 o'clock.ejection pattern. You could get an auto bolt carrier and a SSS Tubs buffer spring. Carbine gas length will have less dwell time which I guess could get you your 1nish eject pattern. |
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The empty casing has been fired and has expanded in size to the chamber. It is now larger than an unfired round and it is normal for it to be hard to extract when manually run through the rifle. This Might also be a little over gassed due to 1 o'clock.ejection pattern. You could get an auto bolt carrier and a SSS Tubs buffer spring. Carbine gas length will have less dwell time which I guess could get you your 1nish eject pattern. I though carbine length had the MOST dwell time. |
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The empty casing has been fired and has expanded in size to the chamber. It is now larger than an unfired round and it is normal for it to be hard to extract when manually run through the rifle. This Might also be a little over gassed due to 1 o'clock.ejection pattern. You could get an auto bolt carrier and a SSS Tubs buffer spring. Carbine gas length will have less dwell time which I guess could get you your 1nish eject pattern. I though carbine length had the MOST dwell time. I'm not a expert and I just worked 7 12 hour shifts in a row ( tired brain), but the dwell time has to do how long the gas system is under pressure due to the relation of where the gas port is located and I believe gas port size, buffer, buffer spring, and BCG can influence dwell time. |
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The empty casing has been fired and has expanded in size to the chamber. It is now larger than an unfired round and it is normal for it to be hard to extract when manually run through the rifle. This Might also be a little over gassed due to 1 o'clock.ejection pattern. You could get an auto bolt carrier and a SSS Tubs buffer spring. Carbine gas length will have less dwell time which I guess could get you your 1nish eject pattern. I though carbine length had the MOST dwell time. I'm not a expert and I just worked 7 12 hour shifts in a row ( tired brain), but the dwell time has to do how long the gas system is under pressure due to the relation of where the gas port is located and I believe gas port size, buffer, buffer spring, and BCG can influence dwell time. Dwell time is the time that the gas system is under pressure from the moment the bullet passes the gas port until it exits the muzzle. Carbine is the longest, followed by mid length and finally rifle length. It is typically agreed on that most 16 inch carbine-length guns are over-gassed so that they have a higher chance of working with a greater array of ammo types. You are mostly correct. I think you just got your definition of dwell time wrong. |
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The empty casing has been fired and has expanded in size to the chamber. It is now larger than an unfired round and it is normal for it to be hard to extract when manually run through the rifle. This Might also be a little over gassed due to 1 o'clock.ejection pattern. You could get an auto bolt carrier and a SSS Tubs buffer spring. Carbine gas length will have less dwell time which I guess could get you your 1nish eject pattern. I though carbine length had the MOST dwell time. I'm not a expert and I just worked 7 12 hour shifts in a row ( tired brain), but the dwell time has to do how long the gas system is under pressure due to the relation of where the gas port is located and I believe gas port size, buffer, buffer spring, and BCG can influence dwell time. Dwell time is the time that the gas system is under pressure from the moment the bullet passes the gas port until it exits the muzzle. Carbine is the longest, followed by mid length and finally rifle length. It is typically agreed on that most 16 inch carbine-length guns are over-gassed so that they have a higher chance of working with a greater array of ammo types. You are mostly correct. I think you just got your definition of dwell time wrong. Thanks for clarification. |
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The 16in. carbine length gas systems dwell time is longer than a 14.5in carbine length gas system,16in. midlength and 20in. rifle length. The 14.5in. carbine length gas system and the 20in. rifle length gas system have the same dwell time. If you measure both the 14.5in carbine and 20in rifle, the distance between the gas port and the end of the barrel are the same on both. |
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The brass deflector just doing it's job. The brass is not making it to the deflector. It is hitting off the front edge of it and bouncing forward. Quoted:
Only problem I see is the BCG is way under lubed. If it is ejecting you have no problem just over thinking it. If you want it to change work with changing the buffer weight. I wiped down the BCG for pictures. I run it dripping wet. Also, it is an A2 buffer, I don't think I have much option in weight. My main concern is not really where the shells are ending up, but I think it is a symptom of a more serious problem. I can not think of a good reason why the bolt carrier would completely lock up when chambering an empty cartridge. If you are trying to chamber an empty case, most of the time it will lock up due to the cases slightly stretching after being fired. That is normal. Your rifle is over-gassed, that's why cases are ejecting at 1 o'clock. Cases are ejecting later than normal during the cycle and being deflected from the edge of the ejection port. You need to slow down the cycle a bit. |
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The 16in. carbine length gas systems dwell time is longer than a 14.5in carbine length gas system,16in. midlength and 20in. rifle length. The 14.5in. carbine length gas system and the 20in. rifle length gas system have the same dwell time. If you measure both the 14.5in carbine and 20in rifle, the distance between the gas port and the end of the barrel are the same on both. +1 Simply stating carbine is longest rifle shortest bla bla is bad info. It's in relation to the barrel length AND gas system length. Not just gas system length. Plus the farther down the barrel you are the less pressure you have so while 14.5" carbine and 20" rifle have the same dwell time. The pressure for the carbine gas system is a lot higher. damn near 15k psi at the chamber difference. |
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Sounds like a break-in issue. Report back after you have put 500 rounds through it. I don't see any issues. I have a gun that only ejects at 1:00-2:00 all the time and runs like a top. But shoot another 500 and report back. You might chamber brush scrub the chamber a little and clean it up. Some chambers show up from the manufactures new full of oily junk and need to be cleaned some. I also have a gun that anytime an empty casing that goes in the chamber for malfunction drills, it takes mortaring to get out. It is just a little tight. Where another gun I have will eject fired brass with the charging handle easily. Just keep the gun properly lubed and enjoy. 
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Make sure the ejector plunger is working freely and the spring is adequately strong. Sounds like the scrape mark is maybe a sharp lug inside the bbl. extension. These shavings accumulating inside the bbl. extension could account for the brass smeared on the outside of the bolt lugs. Your brass is very soft and/or the chamber is rough. Maybe both.
I tried running an o-ring on a .308 extractor and it caused ejection problems. I clip the ejector springs on my match rifles to purposely make them eject to the 1:00 position to prevent pelting the shooter and scorer to my right with hot cases, but I don't like this ejection pattern on any other rifle. Added- retract the bolt with the charge handle and see where the bolt nose stops. It should be even with or slightly forward of the rear of the ejection port. If it is farther back than that, there is something wrong. Most likely the buffer tube depth or an out of tolerance buffer. Have seen a rifle where this caused the last fired case to wind up backwards still inside the receiver. |
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