Occasional failure to lock on empty mag while running suppressed

[nightchief]

Recently, I have encountered occasional failures to lock back on the last round while running suppressed. I haven't been able to pinpoint a particular culprit and am looking for some advice on components to check for cause. Running an 11.5" barrel, with .070 gas port, non-adj gas block, LMT e-carrier, A5H3 buffer with Sprinco green spring. Suppressor is a SF 556-212. Ammo is usually GECO 223 or Fiocchi 223, with occasional Fed XM193, IMI M193 or CBC M193. This issue has been happening mostly with gen 2 p-mags, but I'm not certain its exclusive. I believe the failure to lock back has occurred with the 223 ammo, but not certain.

I tend to use same 6 or so mags when running suppressed, so is it possible the mags have just gooten so dirty the followers are sticking after the last round?

NC

[5.56 Bonded SP]

Does it lock back when not using the suppressor?
How new is your lower, have you used it much before with the current bolt catch?

I have an out of spec lower that needed to be broken in a few hundred rounds before it would lock back, I think something about the mag catch was out of spec, but it got worn in and works 100% now.

[nightchief]

Does it lock back when not using the suppressor?
How new is your lower, have you used it much before with the current bolt catch?

I have an out of spec lower that needed to be broken in a few hundred rounds before it would lock back, I think something about the mag catch was out of spec, but it got worn in and works 100% now.

It locks back when unsuppressed. Lower has somewhere around 5k on it. Probably 2k with the A5 extension. I recently added a G Maritime bolt catch, but the occasional failure to lock started occurring before I added it.

[Cane55]

Are you using standard power A2 spring? The H3 buffer might be too much weight for a .070 gas port to overcome. Try a lighter buffer and see how that works. I always thought that shorties were supposed to have larger gas ports to overcome the lack of dwell time when compared to longer barreled rifles. My BCM 16” mid length has a .078 gas port for example. What barrel manufacturer is it? If your spring is standard power the first thing I would try is a lighter buffer weight. You will definitely be able to solve this issue.

[Cane55]

I just read your second post where you said it locks back unsupressed. Knowing that now it’s possible that when your shooting suppressed your bcg is going too fast and outrunning your magazine spring & follower. Maybe using a heavier weight buffer would slow it down and give the magazine spring & follower enough time for lockback.

[Iraqgunz]

First thing I would do is attempt to determine if it's certain ammo. By reading your post, it appears you are either mixing your ammo, or not keeping track of what's being shot.

Next thing I would do is get some additional magazines and troubleshoot the issue. Considering that magazines are often times the first point of failure with semi-auto weapons, it makes sense.

[nightchief]

First thing I would do is attempt to determine if it's certain ammo. By reading your post, it appears you are either mixing your ammo, or not keeping track of what's being shot.

Yesterdays failure occurred with 55 gr Fiocchi 223 from a gen 2 P Mag; Previous time out, one failure to lock occurred while running GECO 223, the other one form that day I am not certain of, as I was testing some Fed Xm 193, IMI M193 and CBC M193. I don't recall if the other failure occurred with the GECO or the Fed/IMI/CBC 556.


Next thing I would do is get some additional magazines and troubleshoot the issue. Considering that magazines are often times the first point of failure with semi-auto weapons, it makes sense.

Roger. I will try some new mags next time out.

[glockshooter]

My educated guess based on you saying the rifles locks back unsuppressed is that the bolt is out running your mag spring. You could try new mags, heavier buffer, or adjustable gas. It does make sense to short stroke supressed but operate correctly unsuppressed. Maybe you can record it firing to help diagnose your issues.

[Iraqgunz]

With his current set he should not need an AGB. That configuration has been run by quite a few people without issue.



My educated guess based on you saying the rifles locks back unsuppressed is that the bolt is out running your mag spring. You could try new mags, heavier buffer, or adjustable gas. It does make sense to short stroke supressed but operate correctly unsuppressed. Maybe you can record it firing to help diagnose your issues.

[MQ105]

It does sound like you might be a bit over-gassed with the can. Possibly your mags are dirty in combination with older/weaker mag springs, and high BCG speed when suppressed. Sort ammo as already stated; mark mags to determine if one/more are problematic; check/replace mag springs or try new mags.

[nightchief]

Ran the same set up a couple of days ago and had two failures to lock back on an empty magazine. Both issues occurred with the same ammo, the Fiocchi 55gr 223. One occurred with a Gen 2 pmag, the other occurred with a new gen 3 pmag. I'm inclined to believe its the ammo and will test out some 556 next outing with the same mags to verify. I did add a Geissele Maritime bolt catch as well as a ported/vented Radian charging handle (an attempt to lessen the gas to the face), before these incidents occurred. Would either of these changes have enough impact alone, or together, to cause this issue?

[AKDoug]

Ran the same set up a couple of days ago and had two failures to lock back on an empty magazine. Both issues occurred with the same ammo, the Fiocchi 55gr 223. One occurred with a Gen 2 pmag, the other occurred with a new gen 3 pmag. I'm inclined to believe its the ammo and will test out some 556 next outing with the same mags to verify. I did add a Geissele Maritime bolt catch as well as a ported/vented Radian charging handle (an attempt to lessen the gas to the face), before these incidents occurred. Would either of these changes have enough impact alone, or together, to cause this issue?

Ammo and that bolt catch both have potential to cause your issues. I'd really be curious to know the gas port size on that barrel.

[nightchief]

Ammo and that bolt catch both have potential to cause your issues. I'd really be curious to know the gas port size on that barrel.

Not measuredby me, but the Sionics RGP barrel is .070 or .071 depending on who measures it.

[AKDoug]

Not measuredby me, but the Sionics RGP barrel is .070 or .071 depending on who measures it.

Never mind.. I've got two threads in my mind at one time... Forget the gas port comment.