Having a boltover malfunction

[bluedevil008]

My 3gun AR is constantly having a boltover malfunction. I have probably put 1k rounds through it and this has not happened until the last 300ish. I took it apart, cleaned it thoroughly and it is still having the issue (although not as frequently). Last range session was 3 times out of about 100 rounds-ish. Before I cleaned it, it was getting worse and worse until it was once every 5 rounds or so.

This happens in all of my mags (various Pmags that are all in great shape and have worked well before).

I read that this is most commonly caused by a loose magazine catch. So I tightened it when I installed a new mag release button a few days. I am going to the range sometime this week to see if it is running more reliably.

Will chambering a few dozen rounds through the gun before I go to the range come close to effectively reproducing the problem? If it is the mag-issue of course. And when I mean run, I mean chamber, rack slide to eject, repeat.

I don't want to waste another 100 rounds after "fixing" each potential problem. $$$

Other causes according to the internet could be the:

1. feed-ramps (in which case I need to see if it is the same side of the magazine causing the issue each time)

2. the magazine itself

3. ammo (I've ran several hundred of this NEW Fiocchi before with no issue)

Thanks for the help!

[wgj3]

Do you have your gas turned down on this rifle? Give me a call when you have a minute.

[StealthyBlagga]

1) Use some known-good, brass-case factory ammo (M193).

2) Use different magazines (PMAG is the gold standard, so you should be good - try a new one just to be sure).

3) Make sure you have enough gas: Load 1 round in the mag, chamber the round then fire - the bolt should lock open. Repeat at least 5 times to confirm the bolt locks open consistently. If not, you have insufficient gas and so the bolt is not cycling all the way back consistently. We would need to know all the details of your gas system, bolt group and buffer assembly to help troubleshoot.

Edited July 14, 2014 by StealthyBlagga

[Mbauer67]

A friend of mine reciently had the same problem, the issue is the bolt is not traveling far enough back to pick the round. So it could be a couple things, such as not getting enough gas and or a mechanical stop

In my friends case he had a carbine length buffer with a rifle length gas tube, which may or may not work depending on the rifle. But his was compounded by using a heavy aftermarket buffer, we switched to a normal buffer he had and the gun runs perfectly now.

[kurtm]

I'll play! I have a carbine length AR which consistently would short stroke. Went through everything that can be thought of....still short stroke! Got real tired of it so tried it on another lower....ran perfect! Hmmm!! Tried that lower on a different upper....ran great!! Ok so got a bunch (5) other ARs and here is what I found....the Bad upper worked on ALL 5 other lowers. The BAD lower worked with all 5 other uppers.....it just won't work with the upper it came with....ok so switched buffer tubes.....no worky...switched fire control groups, no worky.......pulled out the buffer detent......no worky....so put it all back.....and just swapped another lower for this one......now everything works. So sometimes S.S. isn't just a magazine or gas problem. I can only guess tolerance stacking somehow, and oh HELL yeah I checked for carrier rub, bind, fairy dust...etc.

[assaulter]

A friend of mines rifle started doing that several years ago. He changed the gas rings and it ran perfectly.

[bluedevil008]

Well I've got a multitude of possible problems/solutions.

I'm about to go to the range with new gas rings on the bolt, as well as a different lower and BCG. I will also be trying new ammo, and I may as well bring some steel mags.

I'm sure the combination of that will fix it, I just hope I can find it with limited ammo.

[aquaticvisions]

A friend of mines rifle started doing that several years ago. He changed the gas rings and it ran perfectly.

Me too. My malfunctions looked just like the picture posted. I put new gas rings in (the only change I made) and it has run perfectly with different brands of ammo and different types of mags.

[gerritm]

The rifle I built for my son had this as a random problem. Would only happened every 100 rounds or so. Looked exactly like the pictures. I eventually changed everything from the ammo, bolt, carrier, gas rings, mags, all the normal stuff and it still would happen once in awhile. Finally bought a complete matched buffer tube, spring, and buffer assembly. Replace everything with new and the problem has never happened again.

It was very frustrating because it would always happen during a match, never at the range. could not be duplicated.

gerritm

[bluedevil008]

Just shot a match yesterday (~80-90 rounds) using a different BCG and had no issues. I'm going to buy a LMOS BCG and spring assembly and test it out. I had tried swapping the gas rings on the other BCG and it was still having problems, also tried new ammo and it didn't affect it.