[MississipVol]

I took my Colt LE6920-MP to the range for the first time this morning, shooting a total of 100 rounds.

Although I didn't use the crazy advice from my LEO friend (to pour motor oil down the barrel after the first mag) I DID clean the barrel after the each 20 round mag with Breakfree CLP.

Here is my question:

I loaded each mag with 20 rounds and out of 5 magazines, the bolt didn't lock open after the last round of the 3rd and 4th mag. I know a gun may need to "break in" but wanted to see if this is anything I should be concerned about.

Other than that, there were no other issues whatsoever. No jams or anything. I used PMC bronze 55 grain primarily but did shoot one 20-round box of MFS 62 grain ballistic tipped zinc plated steel cased ammo.

TIA for your responses!!

[Airhasz]

What kind of magazines are causing the problem? Breaking in should have nothing to do with magazine operation.

[MississipVol]

Originally Posted by Airhasz

What kind of magazines are causing the problem? Breaking in should have nothing to do with magazine operation.

I am using the 2 magpuls that came with the gun. But I don't think its a magazine issue is it? The issue is the bolt is not locking back after the last round shot.

[Cole125]

The bolt not locking back is most likely a magazine related issue or;

A. Underpowered ammo

B. Issue with gas system

C. Issue with bolt catch

B and C are highly unlikely with a Colt however.

[MississipVol]

Originally Posted by Cole125

The bolt not locking back is most likely a magazine related issue or;

A. Underpowered ammo

B. Issue with gas system

C. Issue with bolt catch

B and C are highly unlikely with a Colt however.

They are brand new Magpul mags.

I cleaned it and put the bolt assembly back together. Is there a chance I didn't do something right? I mean....it fired fine. Just didn't lock back 2 of the 3 times.

[K. Foster]

Originally Posted by MississipVol

I am using the 2 magpuls that came with the gun. But I don't think its a magazine issue is it? The issue is the bolt is not locking back after the last round shot.

You are using 20 round Pmags?
30 rnd Pmags have an excellent reputation for reliability. However, some 20 round Pmags are known to have that issue from time to time. Use a permanent marker or a paint pen to number your mags so you can easily identify problem mags.

[Trey83]

Next time your at the range, load the magazine with a single round and fire it a few times to see if it locks back. Make sure you're using quality ammo. Also make sure the rifle is lubed up.

My guess is that it's the mags.

[Cole125]

Originally Posted by K. Foster

some 20 round Pmags are known to have that issue from time to time.

I have heard this as well, come to think of it.

OP, next time you go to the range only take your 30 round P mags and see if you have any more issues.

[MississipVol]

Originally Posted by K. Foster

You are using 20 round Pmags?
30 rnd Pmags have an excellent reputation for reliability. However, some 20 round Pmags are known to have that issue from time to time. Use a permanent marker or a paint pen to number your mags so you can easily identify problem mags.

These are 30 round mags. I was just loading 20 in at a time.

I'll definitely try the suggestion to take a shot out of each mag to see if one is giving me the problem. Thanks!

[SCSU74]

Never heard of breaking in an AR? I guess mine got broken in with the 2,500 rds we shot at patrol rifle school. Didn't do anything special other than add slip ewl to the usual spots on breaks. No malfunctions that I can remember. Was using 30 rd pmags fwiw


Sent from my iPhone... which probably auto-corrected something wrong

[WoodenPlank]

"Breaking in" an AR is bunk. Pouring motor oil down the bore is even more bunk, and a good way to foul it pretty badly, I bet.

Mark your mags, and see if it's one or two mags doing it, or if it's across all of them.

What buffer are you using? What ammo?

As others said, load ONE ROUND (and use GOOD ammo - Federal XM193 or XM855, Black Hills, etc), and fire. See if the bolt locks back. Also, see if the bolt catch is engaging the actual bolt face (in front of the locking lugs) or on the carrier itself (behind the locking lugs). The first is good, the second is not.

Give us details of what it does, and we can help find the problem.

[K. Foster]

Originally Posted by MississipVol

These are 30 round mags. I was just loading 20 in at a time.

Noted.