AR bolt help

[LUCKYDAWG13]

i assembled my AR in the spring from day 1 it was hit and miss if the
bolt would lock back after shooting on a empty magazine it locks back
if i do it by hand but if i run it empty it does not lock back 75% of the time
i adjusted the magazine catch in out doesn't seem to help what else could
it be buffer spring ?

 

[a-sheepdog]

Sounds to me like weak magazine springs. The magazine is what should cause the bolt to lock back.

 

[rcmodel]

Assuming it does it with factory ammo, and you are not shooting your reloads?
And assuming it does it with more then one mag?

Insufficient gas to push the bolt all the way back past the bolt catch.

I'd look at gas block alignment on the barrel, as well as bolt key attachment on the bolt carrier.

rc

 

[LUCKYDAWG13]

all i shoot are my reloads my other AR runs just fine but i did just marry 1 p mag
to this AR i will use new one on my next trip also i did buy my BCG used all looks good on it but will switch that out to will do this all one at a time
will use same magazine new ammo just to take that off the list 1st
2nd new p mag 3rd BCG out of working AR

RC what do i look for on the bolt key

thanks

 

[Warp]

Typically when a person is having malfunctions while shooting reloads, it's the reloads.

Try factory ammo and see if the bolt locks back. Just load one round at a time from the magazine to get as much testing in as possible in the shortest amount of time/lowest amount of ammo. You'll find out pretty quick if it's ammo related.


When you say that you assembled the AR, how much of the assembly did you do? Who made the upper/upper parts? What buffer weight are you using? Gas system?

 

[Ridgerunner665]

What rcmodel said....

And also could be the buffer spring and/or the buffer itself or even the bolt carrier...what's the carrier weigh compared to your other AR's? Full auto carrier?

Which buffer are you using?

What's the gas system length?

 

[LUCKYDAWG13]

When you say that you assembled the AR, how much of the assembly did you do? Who made the upper/upper parts? What buffer weight are you using? Gas system

A2 upper receiver made by RRA
BCG and charging handle ? gun show find
barrel R-Guns 20" also R-G put barrel on and gas tube on
A2 buttstock buffer tube spring spacer used gun show find
lower receiver delton LPK psa

 

[d2wing]

You might want to try another A2 spec buffer and spring. Also, the bolt latch could be damaged. Also try the upper on a different lower and/or vice-versa. Other things could be a blocked gas port or tube, weak ammo, and does the bolt move freely in the carrier. I would start with the spring and bolt latch.

 

[hps1]

Make only one change at a time but try factory ammo first.

Regards,
hm

 

[rcmodel]

RC what do i look for on the bolt key

Make sure the two Allen-Head bolts that attach the gas key to the bolt carrier are tight tight and staked in place so they can't come loose.

rc

 

[Warp]

Make sure the two Allen-Head bolts that attach the gas key to the bolt carrier are tight tight and staked in place so they can't come loose.

rc

This.

Also if there are any carbon markings or similar up there see about taking a picture to post, there can sometimes be visual evidence of excessive gas getting by

 

[henschman]

Bolt not locking back usually means the rifle is under-gassed or over-buffered. Since you are using the standard rifle buffer, tube, and spring for a 20" rifle length AR, I would say it is more likely a problem with the gas (as long as you're sure you're not accidentally using a .308 buffer spring or something). When you mention the gas system was installed by someone else it gets my attention. If its a gas issue, it will be either that the gas block is misaligned, or that the gas port is undersized. I would pull the gas block and check these things. To check alignment of the gas block, you can pull the block, remove the gas tube, close the bolt on a piece of empty brass, snap cap, etc. to seal the chamber, and blow air down the muzzle as you move the gas block around on the journal. The spot where you get the most air flow is where the block is aligned, and where it should be installed. To check the gas port size, you can use some pin gauges... or in a pinch, a set of various sized drill bits will get you a rough measurement. Look up some figures for what a 20" rifle length gas port typically measures (I don't know off the top of my head). If it needs to be drilled out, put a dowel down the barrel before you drill it, and make sure you keep the bit straight.

 

[LUCKYDAWG13]

i will check them out and thank you all for your help

 

[Blade First]

What diameter is your barrel at the gas port? If it is .750", the port should be in the .093-.096" range.

 

[LUCKYDAWG13]

just in up date i switched magazines shot over 100 rounds 3 at a time loaded
in new magazine bolt locked back each time using reloads and factory ammo
thanks for all your help