attention troubleshooters

[jonny rotton]

help!!
does anyone have an idea of why this is happening to me??? the bolt is overriding the round as it tries to feed. it gets partially fed but the bolt is not pushing on the back of the case. i then pull back a little on the charging handle allowing the round to pop up a little then it feeds.
any ideas?? oh and it fails to lock back after the last round

[Cloverleaf]

Sounds like your rifle is under gassed and your bcg isn't coming back far enough to cycle the action properly. Do you have an adjustable gas block?

[kmon]

Sounds like your rifle is under gassed and your bcg isn't coming back far enough to cycle the action properly. Do you have an adjustable gas block?

Agree

[Lemonaid]

Better build info will generate better answers. Upper and Lower manufacture, barrel length, buffer weight, magazine used, ammo used, lubrication of bolt, brass ejection direction and distance, markings on fired brass, gas port size, gas block setting, cycling with dummy rounds, etc.

[VASCAR2]

http://bulletin.accurateshooter.com/2014/08/ar-ejector-mod-for-improved-reliability-with-larger-cartridges/

[montana]

Check your bolt carrier gas key screws. Reverse torque your gas key screws at 30 inch pounds. They should remain tight and not loosen.

[tdbru]

factory ammo or handloads? bullet weight? barrel length? gas system?(rifle, midlength, carbine). as others have said, your BCG isn't being pushed back far enough. this can be caused by several things by themselves or a combination of them. as above. too heavy of a buffer. wrong buffer spring, like a rifle spring in a carbine buffer tube perhaps. under loaded ammo, rare with factory ammo, more of a possibility with reloads. anything causing excessive drag on the BCG, like tons of crud in the action that hasn't been cleaned in ages. a partially plugged gas port or gas tube. a incorrectly adjusted adjustable gas block. shooting way undersized bullets (a handloading oops, which i would think would be obvious, but you never know, like loading 25 caliber bullets in the 6.5 Grendel. i wouldn't think that's possible but......)

-tdbru

[Klem]

Jonny,

Sounds like a 'Bolt-over' jam.

If your BCG is not travelling fully to the rear and locking back on last round then the the carrier instead ends up trying to feed the round up the ramp = jam.

Solution

1. More gas
2. Lighter buffer and/or lighter spring
3. Both.

[jonny rotton]

its one of the new group buy 16" barrels in an aero upper with a bcm rail. the bolt carrier is a lightweight nickel boron. bolt is unknown who made it. just a standard spring and buffer. this is not my first build, it may be around my 20th.

[jonny rotton]

and thank you for all the responses!!!!!!

[jonny rotton]

i was shooting wolf and hornady sst factory ammo. the sst's may have functioned better than the wolf. i dont remember for sure. i just did the extractor modification.

[bigdaddyjak]

[LRRPF52]

help!!
does anyone have an idea of why this is happening to me??? the bolt is overriding the round as it tries to feed. it gets partially fed but the bolt is not pushing on the back of the case. i then pull back a little on the charging handle allowing the round to pop up a little then it feeds.
any ideas?? oh and it fails to lock back after the last round

[jonny rotton]

the gas key is tight. i will check the alignment and how well it fits when i take it apart today. thank you for the suggestions!!

[jonny rotton]

the alignment was good. the fit may be slightly on the loose side, its not very tight.