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Posted: 3/21/2010 7:38:24 PM EDT
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I have an AR15, Bushmaster lower older Bravo Company upper, RRA bolt carrier group. I recently had the front sight removed and a free floating rail and YHM gas block installed. I was shooting it at the range a week ago and it was going bang bang bang for about 70 rounds then click. I tried to pull back the charging handle and it would not budge. It took me a considerable amount of force to extract the round. The case has two gouges just below the neck, apparently from impacting the locking lugs in the barrel. There is also a slight scrape on the rim of the case 180 degrees out from the indentations. I put mabye 70 plus more rounds through it with no more problems. Went home and wiped the bolt carrier and upper down and re lubed. I went out shooting again today and on the second round it happened again. Same scenario. After the second time I shot around 120 rounds with no problems. The first time it was with DRS 55 gr .223 the second time it was with some locally loaded 62 gr .223.
Could this be a magazine problem? At first I was thinking mabye something with the gas block, but out of 250 rounds it has only happened twice. What do you think? 
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Does the bolt lock back on the bolt catch after the last round has been fired(catch on the bolt face, and not on the bottom of the carrier alone???
If yes, pull the mags down and CLP clean them. If no, then you got a short cycling problem and the bolt is not fully stroking each time the the rifle is fired, allowing the mag enough time to recover correctly, and the bolt is making contact with the top round in the mag, not behind the rim, but at the middle of the case to try and strip the round out of the mag (bolt comes to rest on top of the mag, with the front portion of the ammo slightly inside the barrel extension. |
| Yes the bolt locks back on an empty magazine, usually. I say that because when the stuck case problem happens it doesn't seem that the bolt is traveling back far enough to lock the hammer. It has only done this twice though. All other times the bolt gets locked back. Would it still be a gas problem since it has only done it twice or a magazine thing? |
| My other thought was this. I have a wolf extra power buffer spring and a SS H3 buffer. Could the buffer spring be stiff enough to cause a slightly underpowered round to not cycle the bolt all the way and not correctly strip the round out of the magazine causing the malfunction? |
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Quoted:
My other thought was this. I have a wolf extra power buffer spring and a SS H3 buffer. Could the buffer spring be stiff enough to cause a slightly underpowered round to not cycle the bolt all the way and not correctly strip the round out of the magazine causing the malfunction? Yes, and the bigger question is why did you go to more buffer mass and greater recoil spring tension? Drop the standard units back in the rifle if you do not have a good answer for the above, and chances are your current problem will go away (read bigger is not always better). |
| I changed the buffer and spring to try and change the ejection pattern so that it would not impact the brass deflector so hard. I will try the original spring. Another question I have is if the new gas block got installed and the gass hole in the block and barrel are not completely alligned would the rifle still fire 250 plus rounds and only short stroke on 2 of them, or would it short stroke more often than that? |
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Quoted:
I changed the buffer and spring to try and change the ejection pattern so that it would not impact the brass deflector so hard. I will try the original spring. Another question I have is if the new gas block got installed and the gass hole in the block and barrel are not completely alligned would the rifle still fire 250 plus rounds and only short stroke on 2 of them, or would it short stroke more often than that? Depends, could be that the misalignment is just enough to choke the system down enough so that it only becomes a problem when you have a less then standard gas pressure round in play. As for changing the ejection path to more forward, play with the ejector spring instead. The way that you have attacked it now is to create a less than stellar cycle stroke, and will cause more problems that it's worth (as you have noticed). |
| The reason I am curious about the gasblock alignment is because I didn't have this issue before the front sight was removed and replaced with a gas block. I am still going to start with a new mil-spec, if you will, buffer spring. I am debating pulling the gas block off and checking the alignment of the gas ports. |
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Quoted: The reason I am curious about the gasblock alignment is because I didn't have this issue before the front sight was removed and replaced with a gas block. I am still going to start with a new mil-spec, if you will, buffer spring. I am debating pulling the gas block off and checking the alignment of the gas ports. Not that I know anything about changing the gas block, but from a scientific experimental point of view, change out only one thing first (and I would start with the buffer spring because it's easier and cheaper) and fire enough rounds to where either the problem happens again or you are satisfied that it's not going to happen again. If you change both the spring and the block, you won't know which thing fixed it, and you could further cause a new problem with messing with the gas block. I would say that if you fire another 200 rounds and it doesn't happen, it was the spring and you're all set. |
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Quoted:
Quoted:
The reason I am curious about the gasblock alignment is because I didn't have this issue before the front sight was removed and replaced with a gas block. I am still going to start with a new mil-spec, if you will, buffer spring. I am debating pulling the gas block off and checking the alignment of the gas ports. Not that I know anything about changing the gas block, but from a scientific experimental point of view, change out only one thing first (and I would start with the buffer spring because it's easier and cheaper) and fire enough rounds to where either the problem happens again or you are satisfied that it's not going to happen again. If you change both the spring and the block, you won't know which thing fixed it, and you could further cause a new problem with messing with the gas block. I would say that if you fire another 200 rounds and it doesn't happen, it was the spring and you're all set. I agree with your methods. I am leaning slight gas block misalignment because I never experienced any problems before the new gas block was installed. I shot at least 800 rounds through it with the same buffer/spring combo with no issues. So I guess I am going back to the last thing that was changed before the problem presented it self. |
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