Gunsmithing M4 failure to extract issues

[eddy]

ok so my armorer doesnt have an answer to this, so im gonna lay it out on here.

me and a couple of the other guys in my company are having issues with failure to extract the fired cartridge and then the next round double feeds. so after dropping the mag and fingering out the unfired round, i let the bolt go forward and try to clear the spent cartridge, the bolt gets stuck, and the only way to clear the round is to slam the buttstock on the ground until the bolt finally unsticks and ejects the round.

we usually use the lake city ammo and occasionally the british ammo where we have a lot of issues, but as of late, we have been using only lake city, and this was the ammo we here having the issues with. our m4s have been through two iraq tours and have been around for about 10 years of training. they have had the yearly and pre and post deployment reset and maintenance.

its probably the extractor, but i cant imagine all of us having the same issues at the same time 6 months after coming back from deployment.

any help will be nice because its really starting to suck during cqb ranges where 10 rounds out of 30 jam up.

 

[scotharr]

Re: M4 failure to extract issues

If multiple rifles that previously worked all start having similar failures, logic would point one to examine the things that they have in common:

1. Ammunition. Have you tried factory 223 ammo? Try a few other types of ammo to see if it is isolated to a particular brand or batch that you recently started using.

2. New barrels. Did your guns all get re-barreled by the same gunsmith at the same time? Maybe the chamber is rough, out of spec, gas port out of spec.

In short, try to find out what the rifles have in common that may be causing them to have the same malfunction. What has changed recently on all the rifles? Ammo? Replacement parts? Gunsmith work?

If you are having trouble extracting spent cartridges, do some tests to examine the chamber. For example, with the lower and BCG removed, try to finger-feed a round fully into the chamber. It should be very smooth and easy to insert. Push the round in firmly, then tilt the upper vertical and see if the round freely drops out. A rough chamber would cause failure to extract issues as would a gas system problem. If the rifle was re-barreled, the problem is most likely one or the other.

Also, when you have a stuck spent cartridge, don't slam the bolt forward. Instead, remove the BCG and use a cleaning rod from the muzzle end to gently push out the brass. Your are doing this to get a feel for whether the casing is actually stuck in the chamber or if the casing freely comes out and the bolt is one with problems. If you have to pound the cleaning rod.....perhaps you have a very rough or out-of-spec chamber.

If you know anyone who reloads and has equipment to check the headspace of fired cartridges, that is a great way to check your chamber dimensions to make sure they are in spec. In short, the measured headspace of a fired round should be a fair amount longer than fresh ammo. Collect some spent casings and have a good reloader compare the dimensions to fresh ammo.

Anyway, those are some of my ideas to try to learn more about the issue.

 

[dmg308]

Re: M4 failure to extract issues

I would first do a complete chamber cleaning with a carbon cleaner and chamber brushes.Followed by a thorough inspection of the chambers for any corrosion or deformations.Next is the obvious check the extractor for wear and replace the extractor spring(make sure the correct plunger is in the spring).Gas rings extractors and springs are wear items and should be changed periodocally and rarely are.
Just reafirming what Scooter posted as I suspect your culpret lie's somewhere in there.

 

[Brain]

Re: M4 failure to extract issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: eddy</div><div class="ubbcode-body"> i let the bolt go forward and try to clear the spent cartridge, the bolt gets stuck, and the only way to clear the round is to slam the buttstock on the ground until the bolt finally unsticks and ejects the round.

they have had the yearly and pre and post deployment reset and maintenance.

its probably the extractor, but i cant imagine all of us having the same issues at the same time 6 months after coming back from deployment.

</div></div>

Given the excerpts above from your original post, I would suspect headspace or out of spec ammo issues.

Having to slam the butt on the ground to free the BCG says to me that there is binding due to excessive pressure against the lugs. If it were an extractor problem alone, the extractor would just skip over the rim without much effort.

Have the problematic rifles checked again for headspace just to be sure, but I'm suspecting the ammo as the same problem is occurring with more than one rifle and concurrently.

Is the ammo you're using all from the same lot?

Same problems with the Brit and LC ammo?

Is it difficult to extract an unfired round?

 

[dj70]

Re: M4 failure to extract issues

I doubt if it'd the ammo. No way will you jam that much up with LC ammo. Just in case make sure you inspect it as your loading up your mags(dented cases, projectiles which may be pushed in and not correct OAL). Replace the bolts as a whole unit. If that doesn't help tell TOP to get on the supply officer's ass and get you different weapons. If he's any kind of a 1st Sgt. he'll get the shit rolling....at least they did in the USMC in Nam.

 

[eddy]

Re: M4 failure to extract issues

thanks for the tips. ill see what we can do. thanks

 

[treylindsey21]

Re: M4 failure to extract issues

We had this same issue once. After nearly breaking a few leathermans forcing the bolt carriers back all day, we figured out it was in fact that specific lot of ammo. The bolts, extractors and headspace were all fine.

 

[Aubrey]

Re: M4 failure to extract issues

Extractors wear. They should have a sharp "tooth" or be replaced. A proper 5-coil spring and black insert (not the rifle 4-coil and blue insert) should be used, and the SOPMOD O-ring around the spring will give extraction a boost.