What is causing this type of malfunction?

OLM-Medic · Oct 26, 2016

This is an example of how my malfunction looks. This is NOT my firearm though. I just used this pic as an example. Mine will shoot the round in the chamber, eject it, and ruin the next live round by crushing it like so:

Bought new Rock River Arms ATH upper
18" barrel with "match" chamber
Supposedly rifle gas system from what the salesman claimed
A2 stock buffer kit installed
CMMG lower
Ammo is usually OTM
Has happened with various 20 round mags
Tried swapping a a spec BCM bolt carrier and though it mysteriously did not fail for a full day of shooting, it then failed in the same way on day two in greater numbers.
I'd say the usual frequency of this malfunction is 1 in 25 rounds.

Besides being a Rock River, would could be causing this? I want to get it fixed.

Fox123 · Oct 26, 2016

Feed ramps?

woodstock · Oct 26, 2016

ammo, dirty gun, who knows? but THAT gun is dirty. :smoke:

from what i see on the outside is a good representation of what is in the inside.

Florida_11B · Oct 26, 2016

I would say it could be a couple of problems:

Excess accumulation of dirt or fouling in and around the bolt and bolt carrier.

Defective magazines i.e. dented, bulged, or a weak magazine spring.

Improperly loaded magazine. I assume you know how to do this properly
Exterior accumulation of dirt in the lower receiver extension.

Fouled gas tube resulting in short recoil.

A magazine resting on the ground or pushed forward could cause an improper lock.

OLM-Medic · Oct 26, 2016

The pic isn't mine, in case anyone missed that. I just used it as an example.

I keep everything clean and lubed. Tried multiple mags.

outrider58 · Oct 26, 2016

Bad mag follower will cause this as well a warn mag spring. A warn mag/mag catch. Do all your mags do this? If so, maybe check the mag catch/release. Make sure it is screwed into the mag release button deep enough. If your brass has two gouges at the neck, it could be feed ramps snagging the cartridge as well. Didn't see your "tried multiple mags" part until after I posted.

clandestine · Oct 26, 2016

Its hard to say without seeing the rifle but here are some guesses:

Bad Mags. Number them and see if you can pinpoint a mag/s

Do you have an aluminum gas block?

Bad Feed Ramps. DONT dremel them unless you remove the barrel from the upper. You dont grind the aluminum ramps in the upper.

Rifle Gas with 18" Barrel and an A2 could be undergassed. You can test this by removing the weights in the buffer to see if it improves. Springco also makes a reduced power action spring to troubleshoot.

Same thing can happen with overgassing. Adjustable gas can be the fix for that.

clandestine · Oct 26, 2016

I know the picture is not the O.P.'s Rifle, but there is nothing wring with the condition of the AR, if anything it needs more dirt.

outrider58 · Oct 26, 2016

clandestine said:
I know the picture is not the O.P.'s Rifle, but there is nothing wring with the condition of the AR, if anything it needs more dirt.

Bolt looked nice and wet. Just looked like a gun that was run hard that day. :thumbsup:

mvee · Oct 26, 2016

I had a rifle(20 inch) that did that. It turned out the gas port in the barrel was drilled too small. I took off the gas block and drilled it with a larger bit and it works great now. I couldn't see what was going on unti I took off the gas block. I tried a lot of thngs before finding the problem.

Erno86 · Oct 27, 2016

mvee said:
I had a rifle(20 inch) that did that. It turned out the gas port in the barrel was drilled too small. I took off the gas block and drilled it with a larger bit and it works great now. I couldn't see what was going on unti I took off the gas block. I tried a lot of thngs before finding the problem.

I believe I had the same condition with one of my AR's, that used corrosive 5.45x39 ammo. I had the "The Devil Himself" - from Duffy's GunRoom, replace my gas tube along with drilling out the gas port.

Magnumite · Oct 29, 2016

was the bullet nose battered or have a cut mark in it, bullet deep seated in the case?

ajusog · Oct 29, 2016

Mag follower. Maybe even a mag spring meant for 30 rounds jammed into a 20 rounder? Also, with stock buffer..... Are you shooting 223/5.56 or 300blk? Stock buffer for 5.56 is, as I've been told by NRA SROs, is different than 300blk....
So what caliber/grain are you usually shooting as your "OTM" ammo

OLM-Medic · Nov 1, 2016

clandestine said:
Its hard to say without seeing the rifle but here are some guesses:

Bad Mags. Number them and see if you can pinpoint a mag/s

Do you have an aluminum gas block?

Bad Feed Ramps. DONT dremel them unless you remove the barrel from the upper. You dont grind the aluminum ramps in the upper.

Rifle Gas with 18" Barrel and an A2 could be undergassed. You can test this by removing the weights in the buffer to see if it improves. Springco also makes a reduced power action spring to troubleshoot.

Same thing can happen with overgassing. Adjustable gas can be the fix for that.

This sounds like a good for a gunsmith, eh? I'm not good enough working with firearms to do this stuff myself.

Devil Dog · Nov 1, 2016

It's probably because he's shooting it upside down.

Sent from my SM-T710 using Tapatalk

Bolts Rock · Nov 2, 2016

clandestine said:
Do you have an aluminum gas block?

Just curious, what's the deal with aluminum gas blocks?

DaemonAssassin · Nov 2, 2016

ajusog said:
Mag follower. Maybe even a mag spring meant for 30 rounds jammed into a 20 rounder? Also, with stock buffer..... Are you shooting 223/5.56 or 300blk? Stock buffer for 5.56 is, as I've been told by NRA SROs, is different than 300blk....
So what caliber/grain are you usually shooting as your "OTM" ammo

The stock carbine buffer for 223/556 is sufficient for 300BLK. OTOH, I run a Spike's T1 in my 300BLK, so it is quieter as I am out hunting deer.

clandestine · Nov 2, 2016

Bolts Rock said:
Just curious, what's the deal with aluminum gas blocks?

It can vary from gun to gun, but the amuminum gas blocks heat and contract at a different rate than the steel barrel. This often can lead to gas leakage. Depending on how gas port size and how efficient the gas system is, you can experience cycling issues.

Its not much of concern for a bench gun that sees low round counts in a shooting sezsion, but a gun that sees moderate to heavy rates of fire will likely have issues with an aluminum gas block.

Bolts Rock · Nov 3, 2016

Thanks. I figured it was thermal differential just wasn't sure if it was gas leakage or coming loose enough to fall off. I think my only AL gas block is on my bull barrel, not a high high fire rate rifle.

What is causing this type of malfunction?

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