New AR build problems, insight (Update: All problems bad mags)

[jasons]

Wimpy ammo + short dwell time (mid-length gas with a 14.5" barrel) = short stroking. (Not always, but often.)

 

[MadRussian]

It's your mags!!!
Relax until you get to the range with some other mags and run them. Bring every mag you have and run them.
If the problem continues then we'll figure it out.

 

[crazymjb]

Update

I was able to replicate the feeding problem consistently using dummy rounds with 3 of my magazines. While they looked to be fine it seems one or in another case both feed lips are slightly bent. What would happen is the back of the round would dip down as it was feeding(front of the feed lip bent) and the bolt would then ride up over the body of the round.

Hopefully my short stroking issue was fully attributable to bad ammo.

I measured the gas port on the barrel of the un-assembled rifle, it lines up perfectly with the gas block I should note the gas blocks all lined up identically on the other 2 that have already been built, and is approximately 2mm in diameter. It also looks like DD may have polished the feed ramps at the factory. The uppers and lowers appear to all be within spec, as do the BCGs.

Mike

 

[crazymjb]

I opened up an extra buffer and cut a wood dowel similar in size to the weights and I plan on trying different combos next time I go to the range. I had to take some material off the bumper so it could be removed from the tube without a vice, and I may a little cotter pin to use in place of the roll pin which is a pain to take out. I'll keep you all posted.

Mike

 

[crazymjb]

Just an update. Went back with another couple hundred rounds of the trash ammo, and known perfect mags, and had zero problems except for one failure to lock back with the 55gr crap, otherwise it ran flawlessly. I didn't even bother trying out my variable weight buffer. As expected it runs flawlessly with all good ammo, and ZERO problems with the good mags.

Mike