Weird AR Malfunctions

[antsi]

OK, new 16" LAR .223 upper.
I bought it in a FTF private sale, so I don't know to what extent LAR will back this up.

The upper is new and hasn't been shot until today.

Don't have my new lower yet, so I "borrowed" one from my match rifle. Williams 2-stage trigger - don't know if that contributed. Never had any issues with this lower, ever.

I was breaking in the barrel, so shoot, clean - shoot, clean - shoot, clean - shoot, shoot, shoot, clean - etc. Total of 12 shots.

9 of those 12 were totally problem free. Actually shot a nice group.

3 of the 12 gave me a wierd malfunction. The malfunctions did not follow any specific pattern of order.

The malfunctions went like this:
1) chamber a round, drop the bolt, apparently goes in to battery
2) pull the trigger - click, no boom
3) gun is jammed with a round in the chamber. can't open the bolt trying with all my might.
4) take lower off. manually recock the lower.
5) re-assemble
most times, re-assembly was totally normal. Once, I had to use the forward assist to get the bolt to go slightly forward in order to assemble the upper to the lower.
6) shoot, totally normal. Bolt locks open on empty mag.

I was wondering if, despite appearences, the gun might not have been going completely in to battery. That might explain why the trigger pull - hammer strike - was not firing off the round.

However, it doesn't explain why the gun would get stuck almost in battery, and be unable to open the bolt.

Could this be a break in issue? These were the first 12 rounds fired from the upper.

Anyone have any ideas what might be going on here?
Any ideas how to fix it?

Appreciate any help here.

 

[ogree]

Bad round of ammunition, It may have swollen or been improperly sized.

 

[antsi]

Ogree,
Happened three times.
Never had an issue with this ammo before.
Also, each round did eventually function fine after removing and replacing the lower.
I guess it is possible, but it doesn't seem likely to be an ammo issue.

 

[MisterPX]

Is the BC correctly assembled?
Does the bolt move freely and lock up without ammo?
Is the chamber clean?

Since you say it's not the ammo.

Reread #5. Sounds like something in the BCG is amiss.

 

[Lloyd Smale]

first thing i would do is go to town with a good chamber brush. You could have a metal shaving or some gunk left in the chamber that is preventing the ammo from chambering properly. then i would look at your ammo. Could even be a bullet seating problem. I bought a case of pmc 762x39 ammo once that wouldnt run in my mini 30 till i seated all of the bullets deeper.

 

[antsi]

Thanks for the replies.

I'm not sure it isn't the ammo - and next time I get away to shoot I'll try different ammos to be sure

MisterPX,
The bolt does move and lock up normally without ammo.
I'm pretty sure I put the BC together properly.

One overlooked issue you note about the chamber being clean - the overall appearance of the upper was that it was assembled dry, without any lubrication. All the parts looked like they just came off the assembly line - clean and dry. Therefore I only lubricated before shooting. Now I'm thinking that may have been a "Duh!" moment because I didn't clean, which I usually do on new firearms before shooting to remove any gunk or preservatives left over from the factory.

I'll do a serious cleaning and try again.

 

[cornbush]

I had the exact same problems once, it was some reloaded ammo that wasn't sized all the way. Ran it through the die again, worked great.

 

[strat81]

Did I miss what brand of ammo this is?

I'm a believer in never using the forward assist unless your life depends on it. Poking holes in paper is not a reason to use the FA. Why? Because you may end up jamming an out-of-spec round further into the chamber.

I had a similar problem with some of my reloads. Out of a particular batch, most were working fine. But then I started getting jams. Turns out I was flaring the shoulder from too much crimp.

I picked up one of these:
http://www.dillonprecision.com/#/content/p/9/pid/25547/catid/3/Dillon_Rifle_Case_Gages

Every .223 round I reload goes through one of them now.

 

[noyes]

I'm a believer in never using the forward assist unless your life depends on it. Poking holes in paper is not a reason to use the FA. Why? Because you may end up jamming an out-of-spec round further into the chamber.

that's a Big +1

 

[jpwilly]

The FA is there for a reason...to jam a round into a dirty chamber. If your chamber isn't dirty you don't want to use the FA.

 

[nbkky71]

Without knowing what kind of ammo you're using, I vote for having some kind of fouling in the barrel extension.

 

[Alleykat]

Other than the fact that you're wasting time and ammo and prematurely aging your AR's barrel, (Per Gale McMillan, "break-in" is a joke!) sounds like bad ammo to me.

 

[antsi]

ogree was right; strat81 and cornbush also nailed it.

Not a gun problem; an ammo problem.

My bad.

Cornbush, do I read correctly that you resized loaded cartridges?

To those who warn against using the FA for this kind of situation, you are making a lot of sense. To be honest, I had never used the FA for any reason at all until this arose.

 

[strat81]

I'm not cornbush, but I have resized loaded rounds.

Lightly lube the case as usual, remove the expander/decapping rod, insert round. Check for proper OAL afterwards to ensure it didn't "squeeze" the bullet out.

And to be clear, I'm not saying the forward assist is useless and should be banished from existence. I am saying that for most civilians in most circumstances, it will generally cause more problems than it solves.

If a chamber is so filthy that rounds aren't feeding properly, I'd be concerned about overpressure situations and extraction problems. When the bolt fails to go into battery, it's an indicator that something is wrong. Bad ammo, dirty chamber, poor lubrication, broken parts, etc.

 

[DBotkin]

I'm just happy the FA is still there. You never know when one of those wood chucks or prairie dogs might charge... every second counts!

 

[strat81]

That's what bayonets are for.

 

[2amencw]

ar malf

you might want to pull the bolt and LIGHTLY steel wool the bolt rail and body to remove the parkerizing crystals. They are very hard and will end up in the chamber and in the gas chamber of the bolt group and potentially cause the malfs. You can hear the crunching if that is the probem. Also scrub out the upper with a softer plasic brush or the crystals will get embedded in the aluminum.use clp.