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Posted: 11/12/2010 2:16:03 PM EDT
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Hi there,
Have put about 700 rounds through my BCM upper the past month, and have had multiple failure to eject conditions every range outing. I'm hoping it's not the ammunition I'm using (Federal XM193 55gr) because I have a ton of it. I'm pretty thorough in my cleaning and liberal with the lubricant, and I clean the rifle everytime I use it. The rifle came with an o-ring that I assume was to be put on the extractor spring if I needed it, but I feel like this shouldn't be necessary. The rifle should run with the already higher tension spring in the extractor. The extraction problem is as such: The rifle will fire multiple rounds through the magazines, and then on a random round, the case will get stuck on the bolt. It clears the chamber and the bolt seems to come nearly all the way rearward, but it becomes necessary to remove the magazine, let the bolt go forward, and then disassemble the upper from the lower, remove the bolt, and forcefully pull the case off the bolt. Do these rifles have a "break-in" period? I don't want to have to call BCM and bother them if they do. Also, this happens on all three of the PMags I'm using, from multiple positions, prone, kneeling, bench, standing, etc. Specs: BCM 14.5" Midlength Upper w/PWSFSC556 Spike's Lower w/G&R Tactical LPK H2 Buffer & other not important stuff Thanks in advance! |
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Quoted: Ejector seems to be fine, there's proper tension when pinching it, and there aren't any broken parts. something is screwed up with your ejector if the round is still stuck to the bolt face when you pull it out of the rifle. take the BCG out of the rifle and try to stick a spent casing onto the bolt. the ejector should push it away with a good deal of force. |
| Wasn't that Colt KB and quite a few stuck casings blamed on XM193? .. I've shot a little of bit of it and had no problems with it but this almost sounds like the casing getting stuck to bolt is possibly out of spec. Do you inspect your rounds for damage/deformities before loading your mags? I don't think the QC was quite up to par on some of the XM193 that has been sold. |
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single loaded round in the mag, the mag inserted with the round charged, (empty mag left in the rifle), fire for effect and confirm that the bolt is locked back on the hold open device afterwards (bolt catch on the face of the bolt, and not grabbing the bottom of the carrier).
If the rifle is stroking correctly, and the bolt did lock back after the last round fired, then lets look elsewhere. Pull the charging handle all the way back and confirm that the face of the bolt does not retract back past the back of ejection port. If the bolt face does retract back past the last of port, then the spent cases are defected back in. Using a spent case cam'd off the extractor, pivot the ejector into the bolt face a few time. There should be strong ejector spring tension, but the ejector travel should not feel to have any binding. Around the extractor spring, install the supplied O ring to add tension to the extractor. Could be that the spent case is being dropped from the extractor claw/bolt face before end of stroke, and when the spent case is not being ejected cleanly out of the port. Lastly, make sure that you are correctly chamber brush cleaning the barrel chamber. Built up fouling in the chamber can cause higher than normal working pressures, and even cause the chamber walls to hand onto the spent case more then normal (why the extractor is slipping off the spent case rim). P.S. Welcome to the site!!! |
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Wow, thanks for all the great responses guys, I really appreciate it. I'll definitely try those tips next time at the range.
Interestingly, when taking apart the rifle and cleaning today, I noticed that when a spent casing into the chamber and releasing the bolt, I simply can't pull the bolt back anymore without either pulling extremely hard on the charging handle and banging the buffer tube on something hard, it simply won't unlock. And sometimes it's bad enough to need to take off the receiver and jamming the bolt back. After doing so, it exhibits the same exact problem as earlier, the brass is stuck on the bolt. Does this help diagnosis? Thanks again! |
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Quoted: Wow, thanks for all the great responses guys, I really appreciate it. I'll definitely try those tips next time at the range. Interestingly, when taking apart the rifle and cleaning today, I noticed that when a spent casing into the chamber and releasing the bolt, I simply can't pull the bolt back anymore without either pulling extremely hard on the charging handle and banging the buffer tube on something hard, it simply won't unlock. And sometimes it's bad enough to need to take off the receiver and jamming the bolt back. After doing so, it exhibits the same exact problem as earlier, the brass is stuck on the bolt. Does this help diagnosis? Thanks again! sounds like you need to scrub your chamber with a brush. |
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Hard to pull the bolt with a live round would be a dirty chamber that needs to be scrubbed with a chamber brush by hand. If you don't own one, now would be the time to pick one up.
On the bolt alone out side of the rifle, load a single round on the bolt face, cam it inwards so the ejector is depressed, then let the round go. It should clear the bolt face as it pivots off, and if not, pull the extractor and check both the bearing lips of the claw, and the rim relief channel just below it (the very edges on the outsides) for burs that the brass may be hanging up on the extractor. Also, if the key bolts are loose ( should be 37 in lbs) or broken(head staked in in place to the key, but the bolt threaded section below snapped off from the head), this could lead to short stroking, and the bolt will not be locking back on the bolt catch when you do the single round mag test. The reason that I bring this up is if the rifle is only lightly stroking where the spent case never clears the chamber, then the expanded spent case is just jammed/wedge back into the chamber (same a loading a spent case that has not been resized, and a really bear to get it back out). |
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Does the extractor have a sharp lip. A sharp lip could bite into the casing rim, overcome the ejector and hold it in place on the bolt face. By the same token a well worn extractor lip would slip off of the casing rim. The o-ring helps the latter condition.
Take the bolt and see if you can snap a round in place, does it stay in place? A sharp extractor lip can cause a clamping action. |
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It sounds to me like the Bolt is out of spec. If I "load" a round onto the bolt with it removed from the rifle, it wants to flip off due to the ejector. If a round is sticking in the bolt face and doesn't flip off, either the ejector is sticking or spring is bad. or, the bolt face is out of spec and the case head is sticking in the bolt face. Try removing the ejector and spring, then seat a case into the bolt. Does it stick?
ETA: Quoted:
Does the extractor have a sharp lip. A sharp lip could bite into the casing rim, overcome the ejector and hold it in place on the bolt face. By the same token a well worn extractor lip would slip off of the casing rim. The o-ring helps the latter condition. Take the bolt and see if you can snap a round in place, does it stay in place? A sharp extractor lip can cause a clamping action. ETA 2: Sorry I'm a slow reader 
Quoted:
On the bolt alone out side of the rifle, load a single round on the bolt face, cam it inwards so the ejector is depressed, then let the round go. It should clear the bolt face as it pivots off, and if not, pull the extractor and check both the bearing lips of the claw, and the rim relief channel just below it (the very edges on the outsides) for burs that the brass may be hanging up on the extractor. |
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