Last round won't throw the bolt back on my AR.

[Kix]

I tried to do a search, but I couldn't find anyhting. Like the topic says, on the very last round the bolt will not lock open. Could this be a gas issue? I'm noticing a lot of blow by down by the gas block at the end of the barrel. The rest of the rounds eject fine and feed fine. Not sure what's up. Any idea's on what one could look for?
The AR is about 4 years old now and has had maybe 2000 rounds through it.

Thanks,
kix

 

[Force_Multiplier]

Re: Last round won't throw the bolt back on my AR.

if you're getting blow by on the gas block, it's an issue.. is it pinned or a clamp on?

 

[joemusso]

Re: Last round won't throw the bolt back on my AR.

check the gas tube and gas block for carbon build up. you could check the recoil spring and buffer to see if it is getting hung up some how.

joe

 

[Kix]

Re: Last round won't throw the bolt back on my AR.

It's got two small allen bolts attaching it from the bottom and a pin at the top for the tube.

 

[Force_Multiplier]

Re: Last round won't throw the bolt back on my AR.

make sure it's straight and tighten the aleen bolts... sounds like gas is leaking.

 

[milo 2.0]

Re: Last round won't throw the bolt back on my AR.

Does the gun do it with all of your mags. Sometimes it is just a magazine issue, weak springs.

 

[M25BeastShooter]

Re: Last round won't throw the bolt back on my AR.

Always check the Bolt Key it tight. Make sure the bolts are torqued down and staked.

 

[Kix]

Re: Last round won't throw the bolt back on my AR.

I'll give all my mags a go and see what results I get. I'll check all the hardware as well. I checked it again and the blow by is coming out in three different places. Back of the block where the tube goes back, all the way around the barrel in the front and out where the pin goes through the block to hold the tube in.

 

[joemusso]

Re: Last round won't throw the bolt back on my AR.

i say clean the block and tube and realign the block.

 

[Force_Multiplier]

Re: Last round won't throw the bolt back on my AR.

try whatever you want... the gas block is leaking (bleeding off gas) which robs the pressure you need to operate the bolt... get that squared away and it'll run fine

 

[wnroscoe]

Re: Last round won't throw the bolt back on my AR.

Kix,

#1. Remove and clean the gas block, barrel OD at gas block, gas tube and bolt carrier group.

#2. Re-install said items but, line up the top of the gas block so it's level with the top of the receiver, tighten the set screws.

#3. Test fire one round at a time with an empty magazine, the bolt carrier group should lock back in the open position each time. Over/under gas will cause it to not lock back.

Some of the LR308 / AR10 rifles are over gassed from the manufacturer, there are adj. gas blocks on the market that will remedy this for you if that’s the problem.

 

[Kix]

Re: Last round won't throw the bolt back on my AR.

Thanks for info! I will pull it tonight, give everything a good douchinh and giver er a go.

Thanks again..

 

[BittenbytheBug]

Re: Last round won't throw the bolt back on my AR.

Is is just with the last round in every mag? If that were the case I'd check mag/springs 1st.Not clear in your post whether it was just the 1 mag or all of them.

 

[KAZ]

Re: Last round won't throw the bolt back on my AR.

Listen to wnroscoe and resolve the leaking block issue first. Regards

 

[Kix]

Re: Last round won't throw the bolt back on my AR.

It's just the last round in the particular mag I was using that won't lock the bolt back.

 

[Elnino31]

Re: Last round won't throw the bolt back on my AR.

Odds are that you have gas leak around the block as others have stated. Curious to know if you've tried changing ammo? Weaker loads can cause this and make you believe there's an issue.

 

[Elnino31]

Re: Last round won't throw the bolt back on my AR.

Odds are that you have gas leak around the block as others have stated. Curious to know if you've tried changing ammo? Weaker loads can cause this and make you believe there's an issue.

 

[memyselfi]

Re: Last round won't throw the bolt back on my AR.

Too eliminate the easiest fix first. slap in an empty mag ( or above mentioned mag in particular), yank the charging handle back all the way a see if the bolt stop / release will lift up locking the bcg. You could have a worn bolt stop / bad mag follower.

I'm not disregarding the gas issue, but usualy if there is that much of a leak the bcg wont cycle back far enough to eject / strip off round from mag.

Just an idea............

 

[rpk762]

Re: Last round won't throw the bolt back on my AR.

Since it is just that one mag you can put a new spring and possibilty of a new follower in it. I have a bunch of cheap mags that will not lock the bolt group back. I just use those mags for blasting.

 

[JonLSU]

Re: Last round won't throw the bolt back on my AR.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kix</div><div class="ubbcode-body">It's just the last round in the particular mag I was using that won't lock the bolt back. </div></div>

Yep, mag issue.