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Posted: 12/4/2017 2:38:52 PM EDT
Hello,
Having a problem here.. If I put in a full magazine and pull the charging handle. First bullet loads fine and shoots. Shell casing ejects and the next bullet to load gets jammed at an angle from the follower on the magazine into the feed ramp with the Bolt Carrier Group rammed half way into the bullet. I then sometimes can't pull the charging handle back to free the BCG, so I have to drop the magazine, pull the charging handle and pull the round out. The jammed bullet usually has a good dent in the middle of it. Or will have a nice drag dent on it. All from the bottom tooth of the bolt. If I clear the jam, reinsert magazine, charge and fire, all good. but Next round is once again jammed. I've tried about 10 different magazines (all preban of different sizes and metal and plastic) This happens about 90% of the time. Occasionally will I be able to fire more than 2 rounds at a time without the jam. So is the BCG coming back into battery too fast and my buffer tube spring too soft? too strong? Is the tooth of the Bolt not bringing the next round into the barrel from the magazine properly? It was working fine a couple of months ago. with maybe only a couple of these FtF jams. Then the last two times out.. Happening more and more. So that's why i brought like 10+ different magazines to see if that was the problem. And yesterday was brutal. 90% failures. I haven't cleaned the gun in a little while. But it's only been a couple hundred rounds. So not that dirty. Ammo is Federal Eagle 223 55g And I have not tried cleaning it yet to see if that makes a difference. BCM Upper Rec M4, Anderson BCG, Daniel Def M4 556 barrel, CMMG Gas tube, Brownells AR-15/M16 MIL-Spec Buffer Tube Assembly Lower is Spikes Multi Any help would be appreciated. Thank you, Jay |
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First step would be to use a single round in the mag and fire. does the bolt stay open? If not, look for gas leak or carbon build up limiting the gas.
Check chamber with a light really good and look for build up. Clean well, take bolt apart and clean well. These would be the first things to check for and obviously try different mags. |
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Still sounds like a mag problem even though you mentioned you tried several...
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All different kinds of Pre Bans from OKay, to Colt, to Orlite.
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In Armorer Courses we teach a simple approach diagnosing issues when a gun isn't working correctly" If it used to work, and now doesn't, then what has changed?
For process of elimination, start with a thorough cleaning of the barrel, chamber using a chamber brush. Once clean, lubricate the 7 bolt lugs and rails of the bolt carrier with a quality lubricant like Slip2000 "EWL" Extreme Weapons Lube. Then try manually cycling rounds through the rifle to see if it works, and if it manually cycles just fine, then try shooting the rifle and see if the problems is gone or is still happening. I have had 3 rifles (From 2 different LE Agencies) cross my path that used to work, then were having a feeding issue from what I believe is the same as you describe. What there rifles were doing is that you could load the rifle, locking it into battery, the firing, unlocking and extracting the empty casing, ejecting it, recocking the hammer, but the new live live round would be pushed off the magazine but only go about 1/2 to 2/3rds of the way forward and stop, with the new live round have a long crease on the case. It didn't make a difference in any of these rifles if it was on the right or left feed ramp, different magazines or ammo didn't make a difference. I could manually cycle a magazine of live rounds through these rifles with no issues, but when I would fire them they would only fire one live round and the feeding malfunction would occur. To diagnose the issue, I degreased all parts & ammunition, then coated everything with Dykem metal dye (You could use a sharpie marker), and manually cycled a magazine of rounds through each rifle, and didn't find anything out of normal for friction. So I went back to the live fire test after recoating everything with Dykem. After firing and having the malfunction occur, what was found to have rubbed off was the bottom of the 2 bolt lugs as the bolt carrier was traveling rearward extracting the empty casing. So upon closer inspection I found a very slight scuff on the bottom of the collapsible stocks on these rifles (All had M4 type collapsible stocks). Being that the stocks had a slight scuff on their bottom side, I visually looked at the receiver extensions while they were mounted on the lower receiver and couldn't see any bend or damage. So I removed the receiver extensions, and compared them to new ones, only to find that in each situation the receiver extension had a very slight upward bend to it (About 1/4" along its entire length). This bend in the receiver extension was just enough to force the bolt carrier to go back end up and bolt lugs down as the bolt carrier traveled rearward, resulting in the bottom two bolt lugs scraping across the top live round in the magazine and creating a crease that would in turn deform the cartridge just enough so it wouldn't go into the chamber. In each case we put a new receiver extension (buffer tube) on each rifle, and they went back to running reliably with no more feeding issues present. Two of these rifles were originally equipped with Sully Stocks, and someone had changed them out for M4 collapsible style stocks of which had been stuck onto something to get bent and cause the malfunction, hence one of the reasons I prefer a fixed stock. CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 |
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Quoted:
First step would be to use a single round in the mag and fire. does the bolt stay open? If not, look for gas leak or carbon build up limiting the gas. Check chamber with a light really good and look for build up. Clean well, take bolt apart and clean well. These would be the first things to check for and obviously try different mags. View Quote Sooo.. I think to help troubleshoot. I'm going to clean the rifle. If that doesn't change anything and same problem persists.. I have a Colt upper on a similar lower that shoots those same mags without issue. I'm going take the BCG from the Colt and see if same problem or works better. That will help me determine if it has anything to do with the whole Anderson BCG or possibly the Gas Key on it. I could also swap the whole lower from the Colt and see if the different Buffer Tube and spring makes a difference.. If you think that's worth trying? |
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Quoted:
I have had 3 rifles (From 2 different LE Agencies) cross my path that used to work, then were having a feeding issue from what I believe is the same as you describe. What there rifles were doing is that you could load the rifle, locking it into battery, the firing, unlocking and extracting the empty casing, ejecting it, recocking the hammer, but the new live live round would be pushed off the magazine but only go about 1/2 to 2/3rds of the way forward and stop, with the new live round have a long crease on the case. It didn't make a difference in any of these rifles if it was on the right or left feed ramp, different magazines or ammo didn't make a difference. I could manually cycle a magazine of live rounds through these rifles with no issues, but when I would fire them they would only fire one live round and the feeding malfunction would occur. View Quote Quick question though. (I am using milspec tube and stock. But being in Massachusetts, I had to pin the stock in one position). How would being able to move the stock back and forth affect the buffer tube? Doesn't it just travel over the buffer tube like a sleeve and lock into place without any function to the tube or spring itself? Or are you saying the wrong size spring was used inside the buffer tube? |
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Quoted: That is exactly what is going on. Quick question though. (I am using milspec tube and stock. But being in Massachusetts, I had to pin the stock in one position). How would being able to move the stock back and forth affect the buffer tube? Doesn't it just travel over the buffer tube like a sleeve and lock into place without any function to the tube or spring itself? Or are you saying the wrong size spring was used inside the buffer tube? View Quote As for a collapsible stock that has been pinned or fixed into one position for ban states, if you can unpin the stock and remove it from the tube, you might be able to see the ibend along its entire length from front to back (especially if you put it up against another tube or a ruler/yard stick). CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 |
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It's always hard to say for certain what's wrong without handling or shooting a gun.
I would do as others said and clean and inspect it good to start with. From what you describe I think it's a good possibility the bottom of your carrier may be causing an issue as it moves rearward. As the carrier slides back it may be scraping across the top round in the mag and knocking it loose or out of position and then as it comes back forward it is unable to grab the round as it should. If this is what's happening it could be a problem with the bottom of the carrier or with the magazine release or even the bolt catch. It could also be a problem with the buffer tube or retainer. It could also be the buffer face / rear of carrier mating surfaces are damaged. Since several mags all do the same thing it is not likely a mag problem but it could still be a mag issue if mags do not sit into the receiver properly. I would cycle rounds by hand fast as you can and see if you can replicate what happens manually. Try to see if the rounds in the mag are effected by the carrier moving rearward. Check the bottom and rear of the carrier for any obvious problems. |
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Quoted: In all 3 rifles that I speak of, all had a bent receiver extension (buffer tube), where the bottom of the stock had been struck on something that caused the receiver extension to bend upwards (As if you are behind the rifle shooting it). This upward bend (about 1/4" total) which ran from the front of the receiver extension (buffer tube), to the back. This malfunction or bend to the receiver extension (buffer tube), had nothing to do with adjusting the position of the collapsible stock on the receiver extension, what it had to do is that the stock had been struck on something which in turn caused things to get bent. The buffer & action spring (buffer spring) would travel forward and backwards in the receiver extension as normal. The problem is that the bolt carrier goes back into the receiver extension (buffer tube), and when it's bent, the bolt carrier will get pushed towards whatever direction the bend makes it, and in these rifles the bent receive extension caused the back of the bolt carrier to go upwards as it cycled rearward, and when the back of the bolt carrier went upwards it caused the front of the bolt carrier to go downward of which resulted in the top of the ammunition in the magazine to get creased by the bottom of the bolt lugs. As for a collapsible stock that has been pinned or fixed into one position for ban states, if you can unpin the stock and remove it from the tube, you might be able to see the ibend along its entire length from front to back (especially if you put it up against another tube or a ruler/yard stick). CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 View Quote |
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Quoted:
Since several mags all do the same thing it is not likely a mag problem but it could still be a mag issue if mags do not sit into the receiver properly. I would cycle rounds by hand fast as you can and see if you can replicate what happens manually. Try to see if the rounds in the mag are effected by the carrier moving rearward. Check the bottom and rear of the carrier for any obvious problems. View Quote If that works fine.. Could bring me into the gas tube/port area for troubleshooting. And I can do it with snap caps in my house tonight instead of waiting to go the range. Don't need to accidentally put a bullet in the foundation wall. Wife would kill me.. |
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Alrighty.. I cleaned the AR thoroughly. It was pretty dirty.
And then I cycled 4 snap caps through it fast and it loaded and ejected flawlessly. Except! I did get it fail a couple of times when I was slow and weak on pulling the charging handle and not coming back with the bcg at full speed. So that being said, if it does fail with live ammo it's because the bcg is not coming back fast enough or going all the way back into the buffer tube.. When I test it at the range, And if I get the same bullet jams. I'll start by swapping the lower to test the buffer spring from another gun. Then work my way to swapping out BCG's and see if that is sole problem. Hopefully its all a part that i can swap out to narrow down. Cause if all of that doesn't work.. it could be the gas tube and that requires a lot more taking apart and break down etc. |
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Quoted:
Alrighty.. I cleaned the AR thoroughly. It was pretty dirty. And then I cycled 4 snap caps through it fast and it loaded and ejected flawlessly. Except! I did get it fail a couple of times when I was slow and weak on pulling the charging handle and not coming back with the bcg at full speed. So that being said, if it does fail with live ammo it's because the bcg is not coming back fast enough or going all the way back into the buffer tube.. When I test it at the range, And if I get the same bullet jams. I'll start by swapping the lower to test the buffer spring from another gun. Then work my way to swapping out BCG's and see if that is sole problem. Hopefully its all a part that i can swap out to narrow down. Cause if all of that doesn't work.. it could be the gas tube and that requires a lot more taking apart and break down etc. View Quote |
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From the description it sounds like classic bolt-over-round.
When everything works, the bolt carrier is all the way back when the magazine spring has shuffled the next round in the mag to the top ready for the bolt carrier to go forward and shove it into the chamber. If the mag spring is weak that top round comes up late and so, the bolt contacts it somewheres in the middle and it ends up with the bolt digging into the case and the bullet somewhere around the feedlip area, bending the round sorta like a bannana. If the rifle is over-gassed OR....the buffer spring is weak OR the buffer is too light it can cause the bolt to sysle too fast and brings about this same issue. Try a heavier buffer, check the spring. Check the mag springs. |
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Short-cycling for whatever reason. Maybe gas tube is loose - pull on it at the gas block/front sight to see if it moves. Look for a roll pin which should secure it. Sometimes certain ammo is not strong enough to function in a particular set-up. Sometimes its a cruddy/poorly-lubricated rifle. Then you have the more bizarre things, some of which have been posted above. Should be quick to determine if the buffer tube has been damaged/dislocated so its dented or not in line with the bore. On a clean, lubed rifle in good condition the action should cycle freely and without excess drag or noise. Sometimes a new rifle will feel draggy so we hand cycle them as fast as possible a few hundred times. This 'bolt-override' jam is fairly common and is usually the result of failure of the bolt to retract far enough to pick up the case head on the way forward. Since it does accomplish this on manual loading, you can basically skip a lot of possible causes and concentrate on clean, lube, and possible gas leak or low-powered ammo. The only other thing in the buffer tube that could cause it would be a recoil spring that is too stiff.
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Ok. Went to the range this morning.
It ran fine for a while. I put it down to work on other stuff. Then FtF started happening again when I went back to it. Ran out of time to start swapping lowers or bcg. Here is a slow mo video of it not picking up next round. Didn't get video of it jamming 2nd round when that happened. (it was hard to shoot left handed and then video righty) Only about 80 rounds through it before the problems atarted. So I'm guessing when it started to heat up. Got dirty. And cooled a little. https://youtu.be/yH3QiclSHVM https://youtu.be/-6H0SfZWFls |
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Didn't get video of it jamming 2nd round when that happened. (it was hard to shoot left handed and then video righty) View Quote CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 |
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Quoted:
Ok. Went to the range this morning. It ran fine for a while. I put it down to work on other stuff. Then FtF started happening again when I went back to it. Ran out of time to start swapping lowers or bcg. Here is a slow mo video of it not picking up next round. Didn't get video of it jamming 2nd round when that happened. (it was hard to shoot left handed and then video righty) Only about 80 rounds through it before the problems atarted. So I'm guessing when it started to heat up. Got dirty. And cooled a little. https://youtu.be/yH3QiclSHVM https://youtu.be/-6H0SfZWFls View Quote Does it lock back on an empty mag? This should be your biggest priority to find out. Strange that it works for so many rounds before the issue starts to happen. Possibly the little bit of grime from shooting is slowing the carrier just enough to start fully short stroking. You may end up needing to enlarge the gas port but I would check and double check any and all things that may be slowing the carrier before all out blaming the gas. |
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You have a weird situation. It appears that the carrier is short stroking but just barely? I say short stroking because I do not see the carrier slamming to the rear, just barely moving to the rear enough to not pick up the round. Does it lock back on an empty mag? This should be your biggest priority to find out. Strange that it works for so many rounds before the issue starts to happen. Possibly the little bit of grime from shooting is slowing the carrier just enough to start fully short stroking. You may end up needing to enlarge the gas port but I would check and double check any and all things that may be slowing the carrier before all out blaming the gas. View Quote Sooo my guess is bcg is not going all the way back. |
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Quoted: From what I can see in the videos show a where the empty case was ejected, and the bolt carrier went forward and locked into battery, then the trigger was pressed again allowing the hammer to go forward and strike the firing pin with no bang due to no ammunition was fed off the magazine and chambered. If you didn't get video of the 2nd round jamming, is there any chance you could post pics of the jammed round, specifically looking for any dings, dents, scracthes, bends in the casing or other marks that would help maybe give an indicator as to where the problem might be? View Quote The have a solid dent right int he side, or a nice gouge going up the length. It's almost as if the round isn't sitting high enough. But since it happens in all the magazines it's not the follower not being high enough. So it would almost be the bolt is traveling too high and just misses the round. But we also know that, that is almost impossible too. Sooo going with the bcg short stroking. Wont know for sure until i can swap the lowers and see if that changes anything. then that means its the buffer and/or spring and not a bcg/gas tube problem. |
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It does not lock back on last round. But it did lock back on empty magazine and manual charging handle pull.. Sooo my guess is bcg is not going all the way back. View Quote View All Quotes View All Quotes Quoted:
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You have a weird situation. It appears that the carrier is short stroking but just barely? I say short stroking because I do not see the carrier slamming to the rear, just barely moving to the rear enough to not pick up the round. Does it lock back on an empty mag? This should be your biggest priority to find out. Strange that it works for so many rounds before the issue starts to happen. Possibly the little bit of grime from shooting is slowing the carrier just enough to start fully short stroking. You may end up needing to enlarge the gas port but I would check and double check any and all things that may be slowing the carrier before all out blaming the gas. Sooo my guess is bcg is not going all the way back. Your bolt may be grabbing the casing from the side of the case with just tension rather than from the rear. If the bolt is pulling a casing from the mag by scraping along the side it would explain the drag marks. If the bolt strips a round but is not actually behind the casing when doing so it will end up slipping off the round before pushing the round into the chamber. Once the round is loose from the mag it will flop sideways and the bolt will smash into the side of it causing the dent you describe. |
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I think I'm on to something..
Was curious about the buffer and spring I used because I can't find the receipt of it. And noticed that the gas tube is carbine length.. The buffer I bought for the colt is carbine length. So why not compare them The buffers are almost identical in weight. 2.965oz and 2.94oz But the colt is 10" spring. And the rifle with the problem is 11.5" I'm using a standard buffer spring in a carbine gas tube. Would explain the extra resistance and the shirt stroke of the bolt.. |
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I think I'm on to something.. Was curious about the buffer and spring I used because I can't find the receipt of it. And noticed that the gas tube is carbine length.. The buffer I bought for the colt is carbine length. So why not compare them The buffers are almost identical in weight. 2.965oz and 2.94oz But the colt is 10" spring. And the rifle with the problem is 11.5" I'm using a standard buffer spring in a carbine gas tube. Would explain the extra resistance and the shirt stroke of the bolt.. View Quote Carbine is used in adjustable type buffer tubes and rifle is used in longer A2 type stock tubes. A 10'' spring would be a carbine length spring and if you are using a carbine buffer in a carbine tube they should all be OK for working together. If the gun is short stroking it can be from several things. Gas port in the barrel to small and not enough gas. Gas port to big and to much gas not allowing the gun to unlock and cycle with the proper timing due to short dwell time. Something binding / slowing the carrier as it moves rearward, possibly even the chambered casing. Buffer or spring causing to little or to much force vs. timing of the round being pulled from the chamber and the carrier moving rearward. If you have access to some other buffers or springs that would be the first thing I would try. Swapping different buffer weights and spring combinations may get it to work. |
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https://www.youtube.com/watch?v=https://youtu.be/yH3QiclSHVM pausing at 00:10 and moving the frame by frame, looks like the bolt face never made it back past the rim of the case in the mag, but even with this, should have stripped the top round out of the mag on the way forward for a bolt over middle of case jam. View Quote And the stock is pinned but adjustable. Here's a pic of the whole rifle. https://www.dropbox.com/s/xbr09105xqbzefu/20171209_111437.jpg?dl=0 |
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The things I do for you people.. Braved the biting cold this morning and hit the range.
21 degrees and with the wind chill i think it was -200. I ran a 30 round magazine through it and it seemed to go off without a hitch. Strange. Decided to shoot the Colt. Then went back to the problem rifle with a fresh magazine, few rounds later, and bingo, got some missed loads, then some FtF jams. Here are pics of some of those bullets. Scrape on one side, dent on the other. And a stuck round. Then I put in a magazine of Wolf Gold and it shot no problem. Went back to original ammo and back to the jams. So it obviously doesn't like the Fed AE 223 Rem 55g FMJ Now I can start swapping parts. Swapped lowers. Both ran fine. Swapped the Buffer tube springs in the lowers and continued to run fine. Swapped everything back and then FtF jams on the problem gun. So I just swapped the buffer and spring again and both continue to work great. Long story short I believe it was the longer spring and weak ammo causing the problems. (The Colt upper shot the longer spring without a hick-up.) So swapping buffer and springs inside each lower is my solution for the time being. Going to leave it dirty and run it a lot more and try and get a lot more rounds through it. Only about 130 rounds today. Atleast until I notice any more hick-ups and then I'll see what swapping BCG's does to it. https://www.dropbox.com/s/86dq1mymnq9cy08/20171213_103447.jpg?dl=0 https://www.dropbox.com/s/nl8li883jj8gq0r/20171213_132050.jpg?dl=0 https://www.dropbox.com/s/qv89in58u6vzlx0/20171213_132146.jpg?dl=0 |
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That's it then. The longer spring is okay as long as it doesn't stack on you and stop the carrier short. but that can't be happening because you can load it and lock back the BCG manually. As I said, some ammo can be too weak for some particular set-ups. There's plenty of good strong ammo to choose from. The PPU (PRVI) stuff is good. Both my ARs like it for accuracy. One with a 1:9 twist likes the 69 gr OTM and the other with 1:7 twist likes the 77 gr OTM.
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