Sig Sauer M400 Enhanced AR-15 - Bolt Not Locking Back After Last Round Problem
- Thread starter Raff85
- Start date
No, that's a lot of mags that would be busted, and one is BRAND new. They also all worked in my friends Norc.
Going to try a bunch of things this weekend.
So should I, or shouldn't I swap parts out from the Norc.? What are the potential problems if I do?
Going to try a bunch of things this weekend.
So should I, or shouldn't I swap parts out from the Norc.? What are the potential problems if I do?
Are you near Peace River?
Okay guys, so I went to the range today and tried a few different types of mags and four different brands of ammo. It was cleaned perfectly before I went.
I wasn't able to have my buddy come with me to swap out parts, but to be honest after a few comments I am hesitant to do that now anyways.
I did however get some video of the problem, and some pictures. Check it out and let me know what you guys think.
https://youtu.be/EftCMRaub3A
https://youtu.be/74Uc55E7Dig
And here is some pictures of some problems that arose.
I wasn't able to have my buddy come with me to swap out parts, but to be honest after a few comments I am hesitant to do that now anyways.
I did however get some video of the problem, and some pictures. Check it out and let me know what you guys think.
https://youtu.be/EftCMRaub3A
https://youtu.be/74Uc55E7Dig
And here is some pictures of some problems that arose.
I believe your gun is under-gassed.
The right way to determine that is to take the gas block off and measure it. And it's honestly not that difficult to do providing you use the correct tools/technique.
I have seen cases where some gas ports are small but will run with Mil-spec or other hot rounds. Then, when you try, let's say, Remington UMC, the gun starts short stroking.
You mentioned trying Federal. Red box or black box ('tactical')? Try the black box if you haven't already. Or try PPU, it's fairly hot.
PMC tends to be on the lower side in pressure in my experience.
But if you want it to feed anything you feed it, it may need the gas port opened up.
The right way to determine that is to take the gas block off and measure it. And it's honestly not that difficult to do providing you use the correct tools/technique.
I have seen cases where some gas ports are small but will run with Mil-spec or other hot rounds. Then, when you try, let's say, Remington UMC, the gun starts short stroking.
You mentioned trying Federal. Red box or black box ('tactical')? Try the black box if you haven't already. Or try PPU, it's fairly hot.
PMC tends to be on the lower side in pressure in my experience.
But if you want it to feed anything you feed it, it may need the gas port opened up.
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Half way through your second video, you tapped your mag and it released the bolt and carrier. Does it do that often? With an empty mag inserted and the charging handle racked, does the bolt and carrier lock back consistently? Once it is locked back, if you remove the mag and smack the side of the gun, does it cause the bolt catch to release? Without slowing down your footage, you will not be able to really tell if it is running slow due to low pressure in the system, but you may be able to confirm or eliminate the bolt catch as the culprit. Given the variety of mags tried and, if those mags work in other guns, I would rule them out as the issue. That isn't to say that the mag catch isn't holding them a little low. You could try shooting while keeping pressure on the bottom of the mag to keep it pressed up into the well.
Personally, I would want to eliminate everything else before digging into the gas system.
-J
Personally, I would want to eliminate everything else before digging into the gas system.
-J
No, it doesn't do that often. It did it that time because the bolt was held at 3/4 of the way back. It wasn't locked back all the way. (Like the second picture I posted after the YouTube videos)
If I have an empty mag and rack it the bolt will always lock back and stay lock backed. If I smack it when the mag is out and the bolt is locked back nothing happens, and it stays locked back as it should.
All the mags work fine in my buddies gun. I also played with the bolt catch with an empty mag with the gun crack in half to see how far it was going up, and I wasn't able to push it up and further and there wasn't any loose play.
Try the bolt out of your buddy's Norinco in it. It won't hurt anything and I'm willing to wager the gun will run fine.
Have you checked your gas key? Also, with the BCG out of the gun, pull the bolt forward and see if it will stand on the bolt face without collapsing downward.
If it ran fine before, it's not undergassed. It's just not using the gas that it's getting properly. Maybe loose gas key or premature gas ring wear.
You're just checking to see if it's loose.
Okay guys, so I went to the range today and tried a few different types of mags and four different brands of ammo. It was cleaned perfectly before I went.
I wasn't able to have my buddy come with me to swap out parts, but to be honest after a few comments I am hesitant to do that now anyways.
I did however get some video of the problem, and some pictures. Check it out and let me know what you guys think.
https://youtu.be/EftCMRaub3A
https://youtu.be/74Uc55E7Dig
And here is some pictures of some problems that arose.
Don't get scared with those anti-ChiCom comments. The three instances where the "Chinese-spec" issues came up were when folks were trying to install new Magpul MOE or railed handguards (like the Daniel Defense) and had a hard time getting the delta ring back, far enough to get the new handguards to slip in. They had to file a little bit off the ends of the new handguards.
My LMT M4 upper is probably Chicom spec as well since I had to file down the end (and circumference) of a new mil-spec handguard to get it past and sit flush in the delta ring.
The other instances was when folks realized that earlier Norcs used pencil barrels with 0.625" gas blocks instead of the more common 0.750" ones or bought mil-spec stocks and found it out it was commercial size buffer tube.
Go figure, the BCGs work fine in other uppers and headspaces properly, their upper receivers fit on my Noveske g2 and DD lowers, heck their triggers even work on American made lowers. The horror!
So take what the ChiCom bashers say with a grain of salt.
If your buddy's Norc bolt headspaces properly, there ain't no reason why your #### will fall off if you used it on your rifle. If you're worried, just use your bolt with his bolt carrier.
As with worn gas rings on the bolts or making sure the gaps don't line up has been proven to be false. It was found that rifles are so over gassed (maybe not in your case) that it will still perform with worn gas rings or if the rings spaces are aligned.
It is possible your rifle could be undergassed and short stroking. It could also be that it is very overgassed and the BCG is outrunning the magazine spring. What direction is your brass extracting?
Have a look at the pic below for a general guideline based on brass ejection.
I noticed you slapping the forward assist, have you had issues with the bolt not closing easily when chambering a round? Unload all ammo and remove the upper from the lower. Work the BCG back and forth. Do you find it stiff to operate? Is the gas key binding on the gas tube? If yes, then your gas key or gas tube might be misaligned. Follow up on warranty work to sort that out or you risk voiding your warranty if you decide to take on the work yourself.
You can also try this: Remove the upper, remove the charging handle and BCG. Get a good wad of paper towel or cleaning patches and plug the chamber of the barrel. Wrap/cup your hand around the brake and make a good seal with your mouth on your hand. With your other hand, put a finger just floating over the end of the gas tube in your upper. Now blow down the barrel. You should feel the air moving around your finger by the gas tube end. It'll probably take you around 1-1.5sec to expel a mouthful of air. If you feel like you're trying to blow up a car tire, you might have a blockage/misaligned gas block.
My troubleshooting suggestion would be:
- Swap uppers with your buddy. (A) Does his Norc upper work flawlessly on your lower? (B) Does your upper work flawlessly on his lower?
If (A) fails and (B) passes, then the problem is related to your lower. Could be out of spec mag catch location or buffer spring/buffer. Swap buffer spring and buffers and repeat.
If (B) fails and (A) passes, then you know it's related to your upper. Check BCG for any binding by moving it back/forth on an unloaded upper. If that operates smoothly, the issue might be misaligned gas block or gas port too small.
You can always try hotter ammo as others suggested. Or, if your rifle is still under warranty, send it in as removing the gas block on your own will most likely void your warranty. I believe MD Charlton is the warranty folks for all things Sig.
If both (A) and (B) fails, well you're in for a bit of troubleshooting (no pun intended) work.
If both (A) and (B) passes, enjoy your new uppers. Just kidding.
Good luck.
Ok, this is what I'm going to go with...the bolt catch is too snug. It should move very easily. How's it feel compared to your buddies? Swap lowers, with your bud, and try that...at least it'll narrow what part is the problem (gas or catch). If it fires fine with his lower, swap the recoil spring out of yours with his and fire it with his spring.
Just some thoughts.
You could take it to a gunsmith and have him play with it. If you're in Calgary, try the shooting edge.
Just some thoughts.
You could take it to a gunsmith and have him play with it. If you're in Calgary, try the shooting edge.
That's not how the actual test is supposed to work and many guns with perfectly good gas rings may fail that way of testing.
You're supposed to take the firing pin retainer, the firing pin, and the cam pin out of the carrier, then hold the carrier with the bolt facing down. The bolt should not fallout of the carrier.
Per the TM 9-1005-319-23&P.
Standing it up or holding the bolt will suffice for a gas ring test. Also a good running AR should function with the gas rings misaligned and with only "one" gas ring installed.
The video demonstrates it is a gas issue.....obvious no? However some do not consider being over gassed which rebounds the bolt either into battery position or after the full recoil stroke. A weak or very cheap (NORC) buffer and spring will do this and bring the rifle "out of tune". The bolt Carrier is to move consistently and not be bouncing back or forth on each stroke.
Under gassed issues can be a result of the front sight becoming misaligned with the gas port hole. I see your setup may be pinned.....is this correct? Is that light mounted to the rail of front sight?
The video demonstrates it is a gas issue.....obvious no? However some do not consider being over gassed which rebounds the bolt either into battery position or after the full recoil stroke. A weak or very cheap (NORC) buffer and spring will do this and bring the rifle "out of tune". The bolt Carrier is to move consistently and not be bouncing back or forth on each stroke.
Under gassed issues can be a result of the front sight becoming misaligned with the gas port hole. I see your setup may be pinned.....is this correct? Is that light mounted to the rail of front sight?
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I decided the bite the bullet so to speak and send the rifle to M.D. Charlton to have work done under warranty.... Shipping was a pretty penny, and I had to take off my ACOG so that will have to be re-zeroed, but I figured maybe it was the best way to address the issue due to the number of suggestions and possible complexities that are surrounding this issue.
Murphy's law will probably prevail and they won't find anything wrong with it, or the problem will be the cheapest part possible....
Murphy's law will probably prevail and they won't find anything wrong with it, or the problem will be the cheapest part possible....
