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Posted: 5/19/2009 2:36:05 PM EDT
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I took my new custom build out to the range for the first time today, and after about 10 rounds, the bolt wouldn't travel far enough to become seated in the chamber. I took it all apart and found that one of the gas rings got shredded (pic below)
http://img.photobucket.com/albums/v68/datboipat/_MG_4739.jpg A little background, the rifle is brand new, put together by me from parts I've gathered all over, the bolt and carrier were assembled by Global Tactical. If you click here it'll take you to the product description, and you'll see that the main parts are made by CMT. The range officers were telling me it was probably the monarch ammo i was shooting, which I know is not the best ammo, but could it really do that much damage after only ~10 rounds? I'm going to email the internet vendor and see if they'll help me out, but it shouldn't cost too much to take it to a gunsmith right? Any other thoughts guys? |
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I got the gas rings replaced today, and the guys at the store said to check the inside of the carrier to make sure its free of any imperfections that might hang up the gas rings. I assembled the bolt into the carrier and there is definitely a fair amount of resistance when I move the bolt in and out. However, this is my first AR and I've never handled any other bolt carrier groups so I don't know what kind of resistance to expect.
I'll describe it as best as I can. The bolt goes in most of the way without any resistance, then hits the part of the carrier where the ID decreases and then it takes a firm push to get it past that. Then, the bolt no longer moves freely and moves only with firm pressure. The resistance seems reasonable since it does need to form a gas seal, but I just don't know whats normal. The good news is that the friction is uniform, and theres nothing that is snagging the rings. Does that sound about right to most people? |
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Yeah, that sounds right to me. I don't know wtf the guy was talking about when he was trying to blame it on the ammo; I've never heard of such an issue with Wolf or any other cheap ammo. I'd say just put it together again with new rings and see what happens.
ETA: You might want to try taking a Q-tip and running it around the area inside the bolt carrier where the rings slide back and forth, see if there's anything back there that catches cotton off of the swab. That area is chrome lined and should be very smooth. |
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when you have the BCG assembled (with cam pin, firing pin, firing pin retainer), how easy or hard is it for you to move the bolt in and out of the carrier.
As far as installing the bolt into the carrier, it sounds normal, my Colt 6920 takes a fair amount of effort to get it in once it hits the resistance you're talking about. My RRAs are much easier, but still pass the gas ring check tests. |
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You can try using a carbon scraper to remove any accumulated material in the bolt tunnel.
It may also knock off or smooth down any rough spots in the bolt tunnel. You can also try using a McFarland one piece gas ring. Did you do a visual check before you shot the weapon or did you load it up and let fly?? Whoever assembled the bolt and carrier may have found the bolt to be very tight when he/she assembled it into the carrier. Instead of twisting it into the tunnel, he/she may have whacked it on a table or bench to seat the bolt and ended up buggering the gas ring in the process. |
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Whoever assembled the bolt and carrier may have found the bolt to be very tight when he/she assembled it into the carrier. Instead of twisting it into the tunnel, he/she may have whacked it on a table or bench to seat the bolt and ended up buggering the gas ring in the process. ^ this. |
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Captains1911 - When its all assembled, it takes a pretty firm pressure to move the bolt in and out. I have to grip it with my thumb and one or two fingers to grasp it securely, and pull with about as much force as you would use to push down the plunger on a soap dispenser.
Milo5 - No I did not take apart the BCG before I shot it, in hindsight, that would've been a great idea since I would almost definitely have seen a problem. At least its encouraging to know that the bcg is the only part on the weapon that I did not assemble myself! The one-piece gas ring looks interesting, I might go with that when I replace the gas rings next time (hopefully many many rounds later) Thanks for the input guys! |
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Another update:
Went to the range today with the new gas rings installed. Shot PMC ammo instead of Monarch this time. Worked beautifully for about 25 rounds and ran into the exact same problem. The resident "gunsmith" at the range was thinking it might have been something to do with the headspace, but upon inspection of a few spent casings, felt that wasn't the issue (although never really checked with a gauge). When asked, I told him the rifle was built and put together from scratch from a parts made by all different companies. Hearing this, he felt that I might simply have eff'ed something up. So thats where I'm at. Either something is wrong with the bolt carrier, or I managed to mess up the rifle through my inexperience. I'm taking it to a gunsmith tomorrow to get to the bottom of this. My fingers are crossed that its the carrier. |
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Another update: Went to the range today with the new gas rings installed. Shot PMC ammo instead of Monarch this time. Worked beautifully for about 25 rounds and ran into the exact same problem. The resident "gunsmith" at the range was thinking it might have been something to do with the headspace, but upon inspection of a few spent casings, felt that wasn't the issue (although never really checked with a gauge). When asked, I told him the rifle was built and put together from scratch from a parts made by all different companies. Hearing this, he felt that I might simply have eff'ed something up. So thats where I'm at. Either something is wrong with the bolt carrier, or I managed to mess up the rifle through my inexperience. I'm taking it to a gunsmith tomorrow to get to the bottom of this. My fingers are crossed that its the carrier. I'm thinking there has to be something wrong with the carrier. Do you know anyone that would let you try their carrier with your bolt in your upper? I am having a tough time imagining what you could have done to cause this. Even if there where a problem with the bolt- headspace or not unlocking fully or whatever, it should move freely inside of the carrier regardless. Good luck. |
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Two things could be causing the problem here.
1. A burr in the bolt tunnel. 2. The through hole on the bolt for the cam pin was drilled off center and the bolt is camming off center causing the rear ring to drag on the tunnel wall.. Try another carrier first and if that doesn't fix the issue, replace the bolt. Actually, you should probably best send the whole BCG back to the parts source and have them replaced. Both parts should be replaceable under warranty with the manufacturer or parts source.HTH Did you headspace the rifle after you assembled it? In some cases barrels are shipped without fully finished chambers. |
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I say carrier as its the same ring posistion getting chewed up...run the bolt with 2 rings and see if it still does it.No worries before the sky is falling crowd chimes in a bolt will run with 1 ring..ask me how I know  something to do with ring gap staggering most likely
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| Gap staggering really doesnt matter because when the bolt goes in the rings compress and the gap closes up.Somethings catchin or its hitting something as its being pushed in cause its bending.Are you pushing the rings on from the rear and snapping them in their groove under hand pressure? |
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Gap staggering really doesnt matter because when the bolt goes in the rings compress and the gap closes up.Somethings catchin or its hitting something as its being pushed in cause its bending. i know, but i was referring to your comment about knowing it will work with only one ring, usually comes up during a ring staggering conversation. Guess it's of, topic, sorry. |
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Another update: Went to the range today with the new gas rings installed. Shot PMC ammo instead of Monarch this time. Worked beautifully for about 25 rounds and ran into the exact same problem. The resident "gunsmith" at the range was thinking it might have been something to do with the headspace, but upon inspection of a few spent casings, felt that wasn't the issue (although never really checked with a gauge). When asked, I told him the rifle was built and put together from scratch from a parts made by all different companies. Hearing this, he felt that I might simply have eff'ed something up. So thats where I'm at. Either something is wrong with the bolt carrier, or I managed to mess up the rifle through my inexperience. I'm taking it to a gunsmith tomorrow to get to the bottom of this. My fingers are crossed that its the carrier. One more question, was it the same ring (front) that bent both times? Please keep us posted, I'm very curious about this one. |
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To those asking, no I did not check the headspace before shooting. I was wondering about it myself but there are people constantly making threads asking the same thing and the consensus is new (in spec) barrel + new (in spec) bolt = GTG so i decided not to worry about it.
Milo5 - Regarding your thought about the through hole in the bolt being off-center, when I disassemble the BCG, the cotter pin and firing pin drop out no problem, but the cam pin won't make that quarter turn without a great deal of force, through the use of either a hammer or pliers. Also, on the cam pin, where it meets the the edge of the bolt, there is an indentation that is not that visible, but i can definitely feel it: http://img.photobucket.com/albums/v68/datboipat/_MG_4748.jpg Do you think what I described supports your theory? It is the ring closest the bolt face that is getting mangled each time, and in the the same position too: 1st time: http://img.photobucket.com/albums/v68/datboipat/_MG_4734.jpg 2nd time: http://img.photobucket.com/albums/v68/datboipat/_MG_4745.jpg As you can see, the damage to the ring is on the side with the extractor. The pictures don't show it, but the damage is on nearly half the ring on the extractor side, with the opposite side intact. Another picture: http://img.photobucket.com/albums/v68/datboipat/_MG_4744.jpg In this one, you can see a sliver of the ring has actually started to shear off. Perhaps this can help someone diagnose the problem? Or maybe just raise more questions... Another question, why would only that one ring be damaged? Why wouldn't the other two rings get mangled too? I know I don't have any pictures of the inside of the carrier, but after looking at it, there is nothing that jumps out as me as causing the problem. Thanks for all the help guys! |
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isnt that a lot of carbon for 35 rounds? Actually, I cleaned in between range trips so thats after no more than 30 rounds. PMC ammo too. i shot 99 rounds of pmc through a new rifle today and it is barely dirty.i wonder why there is so much more carbon? is there alot of carbon in the carrier? |
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Milo5 - Regarding your thought about the through hole in the bolt being off-center, when I disassemble the BCG, the cotter pin and firing pin drop out no problem, but the cam pin won't make that quarter turn without a great deal of force, through the use of either a hammer or pliers. Something must be wrong with either your carrier, bolt, or cam pin (yeah, that's a useful observation I know). On my BCGs, it takes no force to get the cam pin to drop out or go in, and I can easily move the bolt back and forth in the carrier with finger pressure. If you need a hammer or pliers you have a problem here. Since you bought this from GTS, they might have an opinion. I'm sure they will make it right if it is the fault of their parts. I just posted a link over in their industry board suggesting someone take a look at this thread, but you might just want to give them a call directly. |
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I think the excessive carbon might be explained by gas blowing by the mangled ring.
Sorry, I should have clarified, disassembly of the BCG is a bitch only right after I take it out of the rifle. With fresh rings its a cakewalk. I think I MAY have found the problem though guys. There is a TINY burr on the sidewall of one of the two gas ports on the side of the carrier. I created a link on m4carbine.net and I've posted some pictures there. Check it out. |
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The more i look at the pictures, the more I am thinking the through hole is out of specification.
The burr may have been caused by the ring shredding apart. A couple passes with a diamond needle file should clean that up and it should be done before attempting to use the carrier again. See If you can get another bolt and have the rifle headspaced too. |
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If you bought it from Global Tactical, call or email Denny before you go taking a file to anything. Give him an opportunity to make it right. Any burr or imperfection inside the carrier can cause the damage to thr rings you're seeing. /thread. Oh, when you call Denny, don't mention that you posted this problem here prior to talking to him, I made that mistake and he got pissed. He did take care of me though. |
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If you bought it from Global Tactical, call or email Denny before you go taking a file to anything. Give him an opportunity to make it right. Any burr or imperfection inside the carrier can cause the damage to thr rings you're seeing. /thread. Oh, when you call Denny, don't mention that you posted this problem here prior to talking to him, I made that mistake and he got pissed. He did take care of me though. Yeah I can understand that. But I didn't make this thread to say "hey everyone, don't buy Denny's stuff", but to try to figure out what's going on. I don't think I'm going to call him until I know for a fact its the carrier. Because while it looks like thats what's doing this, i really don't think it protrudes into the cylinder that the bolt travels in. I'm going to test another carrier first. |
| Five days of screwin' around when a simple phone call could have solved the problem. If you're not sure that the problem is with the BCG, then offer to send the whole upper to the BCG mfgr/vendor. I'm sure they'll check the headspace for you. Why did you not disassemble, clean and lube the BCG before installing it into and firing the weapon? If you ever fire an M-16 on full auto, you'll appreciate how much work that little bolt (w/rings) has to do - and maybe have a bit more respect for it. Good luck. |
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Five days of screwin' around when a simple phone call could have solved the problem. If you're not sure that the problem is with the BCG, then offer to send the whole upper to the BCG mfgr/vendor. I'm sure they'll check the headspace for you. Why did you not disassemble, clean and lube the BCG before installing it into and firing the weapon? If you ever fire an M-16 on full auto, you'll appreciate how much work that little bolt (w/rings) has to do - and maybe have a bit more respect for it. Good luck. I don't see how trying to get to the bottom of a problem is screwing around, nor do I see how anything I said could be interpreted as lacking respect for any of my rifle's parts. I wouldn't want to send back the bcg if I don't know for sure its broken. Nor would I want to send my upper across the country to a vendor that I didn't buy it from. Thanks for the constructive post, guy. |
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