AR 15 problem/possible solution

[highlander]

I was at my range yesterday burning up some old reloads in my AR 15 when another member came in with a Bushmaster AR(mine is a DPMS) For what ever reason he could not get the rifle to fire in semi auto only single shot as in fire eject case click empty chamber,now this is with factory ammo.
He asked if he could try a few of my reloads
we traded some rounds and lo and behold it functioned perfectly. Tried my lower with his upper same thing bang case ejects pull trigger and click empty chamber. Tried different magazines same thing.
Now I am familiar with how the various types of actions work but I am not that savvy on the peccadilloes of an AR. An answer on this would be helpful should I happen to have the same problem.
I did suggest that he call Bushmaster tomorrow and throw a fit as this is a brand new rifle and it should function correctly

 

[1903Collector]

If I understand your post correctly it sounds like a short cycle, check the gas rings on the bolt,(one possible solution) the little gaps on each ring should be spaced apart around the circumfrence of the bolt. The bolt/carrier will not move to the rear enough to strip a fresh round off the magazine. Also check the manual, Bushmaster has a troubleshooting guide in the back of the book. The fact that your reloads worked in his rifle is kind of puzzling.

 

[Cross-X]

Clean and properly lube before looking for zebras.

 

[Finalygotabeltfed]

Sounds like it was short stroking.

This can happen even when shooting factory ammo that is not of a sufficient powered load and especially in a gun that is new and not broken in.

In addition to checking the gas rings on the bolt, also check the gas key on the bolt carrier to make sure it is tight and the screws haven't backed out.
They should be securely staked in place.

Check for burrs on the bolt locking lugs and barrel extention and for wear marks where the bolt may be dragging on the mag.

Have him run a few hundred rounds of mil spec ammo through it to break in the gun.

 

[andy t]

The gaps on the gas rings is an old wife's tale. It does not matter if there are any/none gaps.
The lubrication/carrier key staking is a good point. AR run best when the bold,gas rings, and carrier are well lubricated.
Perhaps, the gas tube is slightly bent?
You can check for gas tube misalignment:
1. Clear the rifle
2. Detach upper from the lower.
3. Hold the upper vertically and gently lower the BCG into the upper, making sure the carrier key does not bind on the gas tube.

 

[kevin9]

What factory ammo was he using, .223 or 5.56? There can be a difference in power between commercial .223 and mil-spec 5.56 ammo. Did your rifle function properly with his ammo? Did your upper work on his lower with his ammo? Did you notice any difference in functioning of your rifle with his ammo?

As Cross-X says it sounds like the other guy needs to start with a good clean and lube, check for basic alignment and break-in with appropriate ammo.