AR bolt jamming open

[Mark-DuCo]

My AR just started having an issue with the bolt jamming open. When you pull the charging handle you can feel it get tight as it goes back. Its not like a sudden stop more of a bind. It can usually be freed by tapping the stock on my bench. I tore it down and can't find any wear marks, and the buffer moves freely as well as the BCG when I have the upper off. I am fairly new to the AR scene, but I have over 800 rounds through this gun and haven't had any trouble until now itwas mid session as well so I don't think I put anything in wrong last time I cleaned it. Any ideas?

 

[jd4320t]

Has you buffer tube backed out allowing the retaining pin to rub the bcg?

 

[Fargo]

Did it start right after reassembly? Is the buffer tube bent or dented? Have you removed the buffer and made sure there is no debris in there? Also, inspect your lower and make sure there is a blown primber or walked out pin gumming the hammer up against the bottom of the BGC.




?

 

[MDave]

Are you seeing any scratching or wear on the bolt? Take the buffer spring out and the bolt back and forth in the upper and lower. That should help you figure out exactly where the bind is happening. Once you have an idea of that your check the bolt better for scratches or wear marks. you can do the same with the buffer tube. I have seen this when the castle nut backs off the slap plate. This could cause the detente issue JD4320t mentioned above too.

Let me know what you find out!

Couple good pictures of a castle nut and slap plate here.

https://www.ar15.com/archive/topic.html?b=3&f=118&t=545744

 

[Miles42]

A lot of good suggestions here. Have you checked any? Curiousity is setting in.

 

[Mark-DuCo]

It worked fine ladt time at the range and I pulled it out this time and it jammed first shot. Buffer tube is fine and I pulled the buffer and spring out and its clear. Also I cant see any wear on the bcg.

 

[westfork]

charging handle bent? does it slide back and forth freely on a locked open bolt? or does rifle charge fine and then jam when firing?

also check to make sure gas key is tight and not getting torqued around when you are charging rifle as well as checking area where charging handle engages bcg to make sure something didn't get chipped off or bent around in that area to cause a bind?

good luck.

 

[Mark-DuCo]

Charging handle moves freely, I tore it all apart again and put it back together and it isn't jamming anymore, it still feels a little tight in the last inch or so, but I may just be paranoid. I still haven't seen anything that stands out to me.

 

[arctic427]

Have u checked the buffer spring maybe it is binding up in the last part of travel

 

[rvb]

Check the FCG, debris may have gotten in there causing it to bind on the carrier (eg extra stiff disco due to primer frag keeping the hammer from reseting easily).
Check the buffer, specifically the pin that holds the end piece on, sometimes they walk out (I like to stake mine). It can grab the spring.
Bent charging handle?

Hard to spit-ball good ideas w/o seeing the rifle...

-rvb

 

[xHwyLT]

Just a question, is the gun lubed sufficiently? AR's love lubrication, a "little" lube is not going to go a long way in AR's. You have to really lube it up. Start with the basic stuff first then check everything else.

 

[Mark-DuCo]

The gun has plenty of lube, I put more than I usually do just to be sure with the same results. Buffer and spring all look fine and using a dowel rod I can move it freely the full length. I can't find any pieces of a primer, and the hammer is moving freely, no scratches or signs of scraping at all. It does not stick anymore, just feels tight to me.

 

[Mgderf]

You said you have about 800 rounds through it?
You're not even done breaking it in.
Clean it, lube it, and shoot it.

Rinse and repeat.

You might also try a different mag.

 

[Squirt239]

Carrier key canted or bent?

 

[throttletony]

Sorry it's binding up, that's annoying.
I'll agree with the "try a different mag" approach - even a different kind of mag if possible.
does the bolt catch or charging handle have any southpaw modifications?

 

[Mark-DuCo]

No modifications done to it, other than a scope and bipod. It was jamming up with no magazine in place.

 

[Squirt239]

Sounds to me like the carrier key is either canted or bent. Just my ...

 

[Hookeye]

You said you have about 800 rounds through it?
You're not even done breaking it in.
Clean it, lube it, and shoot it.

Rinse and repeat.

You might also try a different mag.

My Stag, BM and RR builds never hung up. Ran fine from the get-go.

 

[joe138]

Is it possible that the carrier key is not staked properly and has become loose?

 

[mvician]

How are you operating the charging handle?

2 fingers straight back or one handed and more than likely pulling it to the one side?