[sammmy]

i recently put together an AR-15 in the last year. i used all dpms components, upper, lower and buttstock etc. i did install a chip mckormick trigger. when i took it to the range, however the rifle would only cycle black hills ammo of 60 grains or higher. i've tried all other types of ammo and the problem is the same: the bolt doesn't travel back far enough to load the next round. i've checked the alignment of the gas block, checked the rings on the bolt, degreased the bolt and bolt carrier. has this happened to anyone or does anybody have any ideas about this? i would appreciate your input very much.

[gamachinist]

Check the gas port in the front sight base (or gas block) to make sure the holes are drilled deep enough into each other and for burrs blocking the holes.
Also check the barrel port for a burr,along with the gas tube at the pin to make sure it isn't restricted.

Check the hole in the bolt carrier for a blockage also.

[1911Tuner]

Bolt carrier key screws staked? Kink in gas tube? Gas port in barrel to spec?

[rbernie]

degreased the bolt and bolt carrierDoes the bolt move freely within the carrier? I was always taught to keep the bolt LUBED, not dry.....

Also - make sure that the upper screw holding the buttplate to the buffer tube is not blocked. If it can't move air in/out of the buffer tube, the trapped air can act as an spring and prevent the bolt/carrier from cycling completely.

[gamachinist]

Good point rbernie,
The upper screw should have a hole in it,and if I remember right ,it is the same length as the lower allowing them to be mixed up.

[sammmy]

thanks for the input, guys. the bolt is lubed, not dry. one of the first things i did was check the gas block, and i noticed nothing unusual about it. i found it to line up apparently ok, and did not look like it was blocked. there was no kink in the gas tube, however i have not yet run a pipe cleaner through it. it's an obvious step. i do not suspect this will solve the problem, though. i'll post back with the results. it'll be a few days

thanks

sam

[JollyWhiteGiant]

Make sure that the carrier key isn't sticking to the gas tube. Also check headspace.