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Posted: 8/26/2012 6:42:37 PM EDT
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Went to the range today with a brand new PSA dissy upper with a new Daniel Defense BCG. Twice in about 100 rounds the BCG got stuck in the chamber on an empty case, once on a MFS nickel coated case, the other on a wolf steel case. Each time I could see the bolt was seted in the. Chamber, had to pop the upper and lower apart, then use a gerber tool to literally pry the bcg out if battery, each time cases looked okay no serious issues, dents, etc. upper was lubed with mpro7.
I was dissapointed to have these issues with quality parts, and the steps I had to take to get it fixed. The sencod time i had to hit the forawrd assist against a bench to try to drive the bcg that last 1/4-1/2" forward so I could open the lower/upper. I don't care if my guns are pretty, but never expect to have to go through this on new parts and was pissed I had to bugger up parts to get things okay. I had no issues with federal or winchester brass but only shot about 100 rounds total! after the second lock up I was pissed and went home. I almost never use wolf but got some in trade so I guess it could be crappy ammo (black box stuff) but I have never had any FTEs with MFS ammo. What could The problem be? Plan to tear it apart and check the chamber out, clean it all and try to run to the range this week if I can but maybe next week due to holiday and work. |
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Could be a number of possible causes. Start with a thorough cleaning of the chamber, barrel, barrel extension (lugs), bolt, extractor, etc, Then lubricate the entire bolt carrier assembly, especially the rails of the carrier and 7 lugs of the bolt (make them wet and glistening like a glazed donut). Checked the headspace to see if the chamber actually measures for 5.56 NATO. I am not familiar with MFS ammo, but most Wolf is 5.56. If your headspace is too tight, then the casing may stick due to the overpressure, and overpressure can cause other issues like the gun blowing up. You may also have a power factor where the ammo is not strong enough. Does the bolt carrier assembly move freely through the upper receiver, and can you manually push the bolt carrier assembly back and forth so the bolt locks/unlocks from the barrel extension (lugs)?
CY6 Greg Sullivan "Sully" SLR15 Rifles TheDefensiveEdge.com (763) 712-0123 |
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Went to the range today with a brand new PSA dissy upper with a new Daniel Defense BCG. Twice in about 100 rounds the BCG got stuck in the chamber on an empty case, once on a MFS nickel coated case, the other on a wolf steel case. Each time I could see the bolt was seted in the. Chamber, had to pop the upper and lower apart, then use a gerber tool to literally pry the bcg out if battery, each time cases looked okay no serious issues, dents, etc. upper was lubed with mpro7. I was dissapointed to have these issues with quality parts, and the steps I had to take to get it fixed. The sencod time i had to hit the forawrd assist against a bench to try to drive the bcg that last 1/4-1/2" forward so I could open the lower/upper. I don't care if my guns are pretty, but never expect to have to go through this on new parts and was pissed I had to bugger up parts to get things okay. I had no issues with federal or winchester brass but only shot about 100 rounds total! after the second lock up I was pissed and went home. I almost never use wolf but got some in trade so I guess it could be crappy ammo (black box stuff) but I have never had any FTEs with MFS ammo. What could The problem be? Plan to tear it apart and check the chamber out, clean it all and try to run to the range this week if I can but maybe next week due to holiday and work. Did you clean it thoroughly before firing it, including the chamber? Check the gas key for proper alignment and staking. Also, check the back of the bolt lugs for excessive wear, could be a headspace issue. Slide the carrier in by hand and check for smooth locking/unlocking. Does the primers on the spent cases show signs of over pressure? ETA: Looks like Sully is already troubleshooting the issue. |
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To tight of head space rears it ugly little head right from the start, with the rig not wanting to stroke correctly from the beginning.
Sully has you lined out pretty will, and I will only add that the chamber needs to be cleaned with a chamber brush by hand, and even more so when steel coated ammo is involved since no standard cleaning agents used on the rifle will dissolve the coatings (has to be scrubbed out instead). 100 rounds and things going pear shape does sound like more of a cleaning and lube problems, so on the note, If you are using Hoppes cleaning solvent to clean the rifle, might want to stop using that. Hoppes leaves behind a residue, and it alone is bad enough to cause the rifle to foul choke out pretty quick, but when it mixes with CLP, even a worse mess. So on that note, CLP should really be used to clean and lube most of the rifle (BreakfreeCLP if you are looking for a source), and to clean the copper out of the bore, then something like Sweets since it does not leave behind a sticky residue that just loves to collect fouling in auto loaders, plus cleans the copper from the bore without the need of a lot of scrubbing. Also, get in a habit of pulling the mags apart and CLP cleaning them as well; even when they are brand new. P.S. to clear the spent case/unlock the bolt, you should not need to remove the upper receiver. Just pull down on the charging handle at the same time that you give the butt stock a hard blow to the ground. If you have a carbine stock, the telescope it in all the way forward first. |
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Everything is brand new, so there was no excessive wear.
I checked everything (chamber, lugs, BCG) for wear, burrs, imperfections etc and see no clear issues. Upper was cleaned before the trip, and lubed well. I am going to try to borrow some headspace guages. The primers looked fine, no different from any other cases I shot. BCG appears to be aligned, staked, and proper. What other signs would I look for with over-pressure? I will clean the whole thing again tomorrow (when I am calmer) and in the sunlight to see if I can identify any issues. I will try to get headspace guages to check out what the issues was. The wolf didn't like to cycle at all really, I didn't have much of it, but it seemed to not want to cycle well (few rounds would go okay) then a FTE. Maybe with a deep cleaning it will work. I was so angry about it though, it took me a few hours to calm down, I wanted to through it down range. 
I will test how the BCG glides through the upper and update. I use MPRO 7 stuff to clean my parts. |
| Stuck cases are from tight headspace. You can file the cam pin cutout in the carrier to the rear and it allows the bolt to move further rearward durring the same time the case is expanding. This sometimes allows an AR to fire steel cases that previously did not. Removing material and polishing the bottom of the carreir will also help stop some drag against the next round in the mag and give more rearward force. |
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Stuck cases are from tight headspace. You can file the cam pin cutout in the carrier to the rear and it allows the bolt to move further rearward durring the same time the case is expanding. This sometimes allows an AR to fire steel cases that previously did not. Removing material and polishing the bottom of the carreir will also help stop some drag against the next round in the mag and give more rearward force. Don't file on the carrier cam slot, all your going to do is cause clearance problems on the cam pin in the upper receiver relief channel. And no, the carrier has nothing to do with head space, its the bolt lugs against the barrel extension lugs that dictates this. |
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Okay, thanks for the replies. still waiting to hear if I can borrow headspace guages locally, but I will run out to the range again later this week and save the spent casings and post pics. Its not a head space problems, since as stated, if you had too tight of head space, the rifle would not want to stroke to even begin with. With the coated ammo, it tension binds to the chamber wall more than brass case ammo , and when the bolt goes to unlock with the spent case still pressure bound to the chamber walls, here is where the problem begins. To make matters even worse, as the chamber begins to fouls out, cause even move adhesion of the coated spent case to the chamber walls, making it even harder for the coated spent case to be extracted. Simply, clean the chamber correctly with the correct solvent and scrubbing,and lube properly with CLP, all will be right as rain. |
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Stuck cases are from tight headspace. You can file the cam pin cutout in the carrier to the rear and it allows the bolt to move further rearward durring the same time the case is expanding. This sometimes allows an AR to fire steel cases that previously did not. Removing material and polishing the bottom of the carreir will also help stop some drag against the next round in the mag and give more rearward force. Don't file on the carrier cam slot, all your going to do is cause clearance problems on the cam pin in the upper receiver relief channel. And no, the carrier has nothing to do with head space, its the bolt lugs against the barrel extension lugs that dictates this. Wrong. For the split second that the bullet has not passed the gas hole in the barrel the lugs are all that matter. After the gas travels to the carrier and the bolt is feeling force from both directions the cam pin does decide how far rearward the case is held against the chamber. I have actually compared different carriers that did cycle steel and did not cycle steel. Yes, it is the carrier that decides and the ones that do not allow enough rearward movement of the bolt durring the innetial turn of the bolt out of battery will cause stuck cases and short stroking. The short stroking is from the case sticking just enough to slow the bolt as it travels rearward even if it did not fully stick. I realized this because I had two AR's that would not cycle steel but if I switched bolt carriers from my rifles that did cycle steel they were both able to cycle it as well. After realizing my rifles cycled steel if they used a different carrier I compared the differences in the carriers and realized the cam pin was holding the bolt more foreward on both of the carriers that would not cycle steel compared to the ones that did. I then milled the two carriers cam cut outs to the same position rearward as the carriers that cycled steel and sure enough the carriers that originally would stick steel cases began to cycle steel perfectly. You are correct about the bolt lugs setting headspace but they do not set the headspace of the casing for the entire durration of the fired round. I am sure there are times the chamber is cut for .223 and will never cycle steel but the info I offered is correct. |
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Stuck cases are from tight headspace. You can file the cam pin cutout in the carrier to the rear and it allows the bolt to move further rearward durring the same time the case is expanding. This sometimes allows an AR to fire steel cases that previously did not. Removing material and polishing the bottom of the carreir will also help stop some drag against the next round in the mag and give more rearward force. Don't file on the carrier cam slot, all your going to do is cause clearance problems on the cam pin in the upper receiver relief channel. And no, the carrier has nothing to do with head space, its the bolt lugs against the barrel extension lugs that dictates this. Wrong. For the split second that the bullet has not passed the gas hole in the barrel the lugs are all that matter. After the gas travels to the carrier and the bolt is feeling force from both directions the cam pin does decide how far rearward the case is held against the chamber. I have actually compared different carriers that did cycle steel and did not cycle steel. Yes, it is the carrier that decides and the ones that do not allow enough rearward movement of the bolt durring the innetial turn of the bolt out of battery will cause stuck cases and short stroking. The short stroking is from the case sticking just enough to slow the bolt as it travels rearward even if it did not fully stick. I realized this because I had two AR's that would not cycle steel but if I switched bolt carriers from my rifles that did cycle steel they were both able to cycle it as well. After realizing my rifles cycled steel if they used a different carrier I compared the differences in the carriers and realized the cam pin was holding the bolt more foreward on both of the carriers that would not cycle steel compared to the ones that did. I then milled the two carriers cam cut outs to the same position rearward as the carriers that cycled steel and sure enough the carriers that originally would stick steel cases began to cycle steel perfectly. You are correct about the bolt lugs setting headspace but they do not set the headspace of the casing for the entire durration of the fired round. I am sure there are times the chamber is cut for .223 and will never cycle steel but the info I offered is correct. If you are attemptting to create more inertia on the carrier as a means to apply more force to unlock the bolt, filing the cam channel on the carrier is not a good solution. Changing to a lighter buffer or reduced spring would achieve the same effect, without the possibility of excessive wear. Also, when changing the distance of travel before unlocking, the carrier can ping the hammer without having a constant rate of force. Almost like a reverse bolt bounce, so to speak. |
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Wrong. For the split second that the bullet has not passed the gas hole in the barrel the lugs are all that matter. After the gas travels to the carrier and the bolt is feeling force from both directions the cam pin does decide how far rearward the case is held against the chamber. Working pressures of the round are in the 55K psi pressure range. Round gets ignited, and the bolt is driven back against the face of the barrel extension lugs via the expanding case, plan and simple. There is enough slop in the carrier cam slot to cam to allow this to happen. As the bullet passes the gas port, gas is driven to the carrier gas chamber section to pressure the gas chamber section to force the back of the carrier gas chamber and back of bolt away from each other, then which in turns unlocks the bolt via the cam. Even if you have a tighter carrier slot, and the carrier is blown or moved back a hair off of the barrel extension face from either pressure blow by, or normal bolt rearward movement tight to the barrel lugs, the carrier is still not going to unlock the bolt until the gas section of the carrier is pressurized by the gas tube. Simply, this is not a delayed blow back action, and gas pressure or force to the bolt does not unlock the bolt in any way. Both the bolt lugs and barrel extension lugs are squared to each other, So until the carrier gas chamber sees pressure from the gas tube, the carrier is not going to unlock. And to see all this, lock a bolt home, drop a cleaning rod down the muzzle, and put pressure to the face of the bolt. You will see that even with pressure against the bolt face, the carrier is still tight against the face of the barrel extension. If the carrier is driven back from the barrel extension face with bolt face pressure, then the entire rifle needs to be sent back to the manufacturer since something is way, way out of spec. |
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Wrong. For the split second that the bullet has not passed the gas hole in the barrel the lugs are all that matter. After the gas travels to the carrier and the bolt is feeling force from both directions the cam pin does decide how far rearward the case is held against the chamber. Working pressures of the round are in the 55K psi pressure range. Round gets ignited, and the bolt is driven back against the face of the barrel extension lugs via the expanding case, plan and simple. There is enough slop in the carrier cam slot to cam to allow this to happen. As the bullet passes the gas port, gas is driven to the carrier gas chamber section to pressure the gas chamber section to force the back of the carrier gas chamber and back of bolt away from each other, then which in turns unlocks the bolt via the cam. Even if you have a tighter carrier slot, and the carrier is blown or moved back a hair off of the barrel extension face from either pressure blow by, or normal bolt rearward movement tight to the barrel lugs, the carrier is still not going to unlock the bolt until the gas section of the carrier is pressurized by the gas tube. Simply, this is not a delayed blow back action, and gas pressure or force to the bolt does not unlock the bolt in any way. Both the bolt lugs and barrel extension lugs are squared to each other, So until the carrier gas chamber sees pressure from the gas tube, the carrier is not going to unlock. And to see all this, lock a bolt home, drop a cleaning rod down the muzzle, and put pressure to the face of the bolt. You will see that even with pressure against the bolt face, the carrier is still tight against the face of the barrel extension. If the carrier is driven back from the barrel extension face with bolt face pressure, then the entire rifle needs to be sent back to the manufacturer since something is way, way out of spec. We could try to compare what pressures do to the carrier, bolt, and extension and make sense of the PSI to air release holes and gas leakage and neither one explain why it works or shouldent work. I can tell you without a doubt that milling the cam cut out to the rear will allow carriers to cycle steal that once did not and does not create any wear in the cam relief of the receiver. |
| If the rifle is attempting to extract the casing but not being completely successful that may indicate under sized gas port,under powered ammo,rough or dirty chamber walls. One other thought,make sure your using a carbine recoil spring and buffer in a carbine and a rifle recoil spring and buffer in a rifle. |
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