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Posted: 11/22/2010 6:40:33 PM EDT
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Yesterday, I had the opportunity to fire my preban PWA M4-type for the first time. It was my second time firing a carbine AR (I have always shot rifles), and I enjoyed it as I got used to the different feel. However, I had an intermittent problem that was really perturbing me. A number of times, with both quality brass cased and steel ammo, I had the bolt retract leaving the empty case in the chamber. The case was easily extracted by dropping the bolt on it and pulling back the charging handle.
I believe that this most likely a problem caused by the plastic buffer. I intend on replacing it with a LMT Carbine (H) Buffer. The extractor and extractor spring seem good, but might be worth looking at if the buffer swap doesn't work. Is there anything else that I am missing? |
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Quoted:
Yesterday, I had the opportunity to fire my preban PWA M4-type for the first time. It was my second time firing a carbine AR (I have always shot rifles), and I enjoyed it as I got used to the different feel. However, I had an intermittent problem that was really perturbing me. A number of times, with both quality brass cased and steel ammo, I had the bolt retract leaving the empty case in the chamber. The case was easily extracted by dropping the bolt on it and pulling back the charging handle. I believe that this most likely a problem caused by the plastic buffer. I intend on replacing it with a LMT Carbine (H) Buffer. The extractor and extractor spring seem good, but might be worth looking at if the buffer swap doesn't work. Is there anything else that I am missing? No, you got it and does sound as if the action is opening too fast with the spent case still too pressure bound to the chamber walls to be pulled cleaned. While waiting on a new buffer, you may want to try to add a #60 O ring (about a dime from any hardware store) around the extractor spring to add tension to it and the extractor. If the above it true with the action openning way to fast, then the rifle should end up either short stroking (will not lock the bolt back on a single mag loaded/charged/fired round), or the rim torn off the spent case. It the O ring does solve the problem and not either of the above happening, then although a standard true buffer should help, suspect that either the extractor or buffer spring may be in question since they are dropping the case with a semi normal stroke. |
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Hello
new to the forum & newbie question here... had similar issue with "... the bolt retract leaving the empty case in the chamber. The case was easily extracted by dropping the bolt on it and pulling back the charging handle." I noticed the rim of spent shell was "ripped" where extractor claw has. Have Bushmaster XM15 lower and S&W 5.56 upper using both Winchester 5.56 & .223; also PMC .223 all gave same result. Any idea? Also is there difference between "CAR 15" and "Standard" AR15 bolt carrier? Reason I asked is my original AR15 has A2 stock and 24" barrel; bought the S&W complete flat top upper and used my Bushmaster lower replaced A2 with CTR and S&W upper. I compaired BC and noticed slight difference in bottom cut of BC, BC that came with S&W has more metal than one i have on Bushmaster Thanks in advance for any help. Arlie |
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The buffer is first off, a length spacer.
A telescoping stock has a shorter receiver extension (tube) than a full lenght stock rifle, so the carbine buffer and spring is shorter. Now having said this, you do not want to use a telescoping buffer in a full length/fixed stock receiver extension since instead of the bolt being limited out correctly in the back stroke, the back of the carrier key just crashes into the back of the lower receiver (read cracking it). Same goes the other way around, with a A-2 buffer used in telescoping stock, the bolt will not make it back far enough correctly strip a round out of the mag. Also to point out, a telescoping recoil spring will be around 10.5", while a A-2 recoil spring will be 11.75" long. If a telescoping spring is used in a full length stock, then the spring tension will be way weak, and cause problem. The other way around, the longer spring coil binds up before the end of stroke, and you end up with short stroking problems. To add here, it's not the upper in play that will dictate the needed buffer and spring, but the length of the recoil extension only (the stock tube lenght). Link to buffers, http://www.biggerhammer.net/ar15/buffers/. As for B/C's , they are the same length, with the only real difference being if the FP is shrouded or not and if for semi or full auto (trip ledge distances from the back of the carrier), which will add some weight. |
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thanks for quick response.
forgot to mention barrel length is 16-18" i have "mil-spec" receiver extension length = 7.25" per magpul tech note CTR-001 installation sheet. I could only assume (i know that's a bad word) the buffer & spring are both "regular" carbine specs. based on what i have read and pictures seen on forum/web. Receiver tube (metal w/ 3 point stops), buffer and spring (most likely off brand/no brand) came with retractable magpul ctr stock when I bought ctr. so you recommend "H" buffer? "a length spacer" - I'm not sure what it is, add length to receiver tube? thanks again for your help. |
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Think of length spacer as the amount that the buffer needed to be allow the B/C Face to come back just short of the back of receiver extension.
Yes, carbine buffer and carbine spring (10.5") for the tube/stock you have. Rims getting torn off the spent case is either an over gas port gas pressure problem that a heaver buffer will help to slow the unlock down to the point that the barrel residual pressure is dropped correctly before the spent case is pulled, or you just have a dirty chamber that has not been chamber brush scrubbed/cleaned correctly, and/or you are using the wrong type of cleaning and lube solvents, and the chamber is fouling out too quickly. |
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I'll install H buffer and report back..
as for cleaning - i normally use a "special" ss brush for where bolt lock up; .308 or 9mm copper bore brush as chamber brush, .22 for barrel, Hoppes #9, rinse with Birchwood Gun Scubber and lube with Breakfree CLP is this acceptable with ARs? thanks again |
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An AR chamber brush will save you a lost of steps since it's chamber and barrel extension shaped to begin with.
As for cleaning, something like Sweets for the bore (does not leave behind a residue), and CLP for everything else (just think of everything besides the bore as getting an oil change since CLP had a cleaner in it that will clean the powder fouling). I like to clean the bore first with sweets, then attack the chamber and barrel extension with CLP, finished off with dry patches down the barrel from the breach. Even through you are dry patching the bore, there will be enough CLP left in the bore for a protective short term storage. |
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Dano523, got my H buffer from BCM and worked like a charm after breaking in. no more ripped rims (once - 1st or 3rd 5.56 round none on .223); fired around 500 rds. question: sorry off topic - i have 5.56 (stamped on barrel ofS&W M&P upper); so is it really or how bad is it to use .223 on it?
also did noticed "heavier" kick with 5.56 but nothing to cry about. thanks so much for your help. i'm about ready to hand this rifle to my daughters for them to enjoy. |
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A 223 chamber is tighter than a 5.56 Nato chamber (end of chamber cut), so shooting 223 ammo in a Nato chamber is not a problem. It would be the other way around that would cause high working pressure conditions.
Better yet, few commercial ammo's are even loaded to Nato spec, and chances are, you have been shooting 223 ammo all along. |
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Dano523,
sorry off topic - promised last post here about rounds/ ammo. "...few commercial ammo's are even loaded to Nato spec, and chances are, you have been shooting 223 ammo all along. " - that's interesting, so I guess one can not really trust what labelled on packaging? I was using Winchester white box marked 5.56; PMC 5.56 - green tip (x-TIP, can not remember exact wording / description on box) and Remington .223 (green/white box) - now I understand why people post even LOT #s of ammo used. I'll look at rest of forum where they cover ammo and learn some more. Man too much to learn when shooting ARs, I'm glad this forum here for noobs like me. I'll also look at membership to support it. Thanks again. Arlie A. |
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