Bolt Locking Issues Question

[Jethatsme]

On one of my semi-auto 18" 223 AR's, the bolt seems to have a hard time locking when cycling the next round. It happens with a few different types of ammo that I have run through it but not all. To temporarily fix the issue, I either put the charging handle back slightly to give it another kick OR I have to drop the magazine, removed the round and re-seed.

What do you think might be the cause?

- Do I need a different gas tube/block (I have a Mid-length Gas Tube, unknown gas block specs)
- Is it a bolt issue where I may need a heavier/lighter bolt


As a note: I clean my rifles pretty regularly so unlikely due to fowling of the components.

Thanks!!

 

[smokin.338]

Have you tried just hand cycling the rounds through the rifle ??
Also what buffer and spring are you running ?

 

[Servo93]

With the safety on and rifle pointed in a safe direction, chamber a round slowly and use the forward assist to push the bolt fully into battery. It should snap shut with a little force.

Having said that ; to me it sounds like a weak buffer spring. They are cheap an easy to replace.

Also, just out of curiosity, how many rounds have been fired through this rifle?

 

[GH41]

Does just it do it on the first couple of rounds of a full magazine? Who's magazines are you using? Does it happen with multiple magazines?

 

[GH41]

Just re read the opening post... "As a note: I clean my rifles pretty regularly so unlikely due to fowling of the components" These rifles like to be run wet. Especially when new. They also like thin lubricants. Not trying to start a lube war but it's hard to beat Break-Free CLP.

 

[Jethatsme]

With the safety on and rifle pointed in a safe direction, chamber a round slowly and use the forward assist to push the bolt fully into battery. It should snap shut with a little force.

Having said that ; to me it sounds like a weak buffer spring. They are cheap an easy to replace.

Also, just out of curiosity, how many rounds have been fired through this rifle?

I have fired probably around 2000 rounds through the lower. It is a separate upper. The upper has seen 250 rounds. Had issues day 1 with it. That's why I thought it might be the gassing or bolt.

 

[Jethatsme]

Does just it do it on the first couple of rounds of a full magazine? Who's magazines are you using? Does it happen with multiple magazines? [/QUOTE I use the Mapgul Genlll mags. I have another 18" upper and 16" upper that work flawlessly with the lower and mags. It's this upper that is giving me some issues. That's while I ruled out some other causes. Does the type of gas block installed on the rifle affect the ability for excess gas to cycle the bolt stronger? Perhaps the diameter of the port hole is too small?

 

[Strikerkc]

I've seen that sort of issue caused by the gas tube in the chamber being a little bent. So instead of slipping cleanly into the gas key on the BCG, it smacks into it, and is pushed into place, instead of sliding.

That last moment resistance can take enough ooomf out of the forward motion to prevent going into battery.

Just take a look at your tube inside the chamber, and at the gas key on your bcg. If either or both look like they're wearing at the ends, or the gas tube looks bent, that's likely your culprit.

 

[Yondering]

On one of my semi-auto 18" 223 AR's, the bolt seems to have a hard time locking when cycling the next round. It happens with a few different types of ammo that I have run through it but not all.

Nobody's asked the most obvious question yet - does the bolt lock up correctly and easily without ammo? When it doesn't lock up correctly with a round in the chamber, is that round hard to extract? If yes to both, the problem is most likely related to the barrel's chamber being too tight for that ammo.

Occasionally you'll see a really tight chamber in an AR barrel that does this. I've encountered it a couple times, both were with Rainier Ultramatch barrels, where some factory ammo just wouldn't chamber, and handloads required a small base die. Yours doesn't sound like it's that bad, but might be just a little on the tight side, either slightly short headspace or tight diameter dimensions.