Picked up an AR recently and finally got to shoot it yesterday. First five rounds ran fine. (this took some time, sighting in scope and moving targets around, etc), then it started to short stroke.  It was pretty cold, probably around 20 degrees. Pulled the buffer and it was very heavily coated with grease so my initial tought is that the grease and the cold is causing the buffer to funtion improperly. Cleaned it up last night and will shoot it again tomorrow.  My other thought is that the JP adjustable gas block needs to be opened up.
Any thoughts on this matter?
Sorry about any typos, less than four hours of sleep a night since wensday is killing me.
Thanks,
Matt

Think I solved the problem.
The adjustment screw on the gas block was all the way out.  I wasn't sure where it was set at but when I found I could turn it completely out with my fingers in about one turn I figured it was too loose. Turned it down a bit and volla. Shoots like a champ now.
Matt

Quoted: Think I solved the problem. The adjustment screw on the gas block was all the way out.  I wasn't sure where it was set at but when I found I could turn it completely out with my fingers in about one turn I figured it was too loose. Turned it down a bit and volla. Shoots like a champ now. Matt

Matt, just as an FYI, JP's instructions say to turn the screw all the way in, and back it out two turns. Load one round into a mag and fire it. If it malfunctions back it out a bit and try again.

Just adjusted a friends JP gas block. We started two turns out, all was well so we turned it in. Ended up leaving it at a turn and a half from fully seated. Locktited it down. The whole object being to get the lighted recoil possible without malfunctions.

The JP adjustable gas block is a very cool idea, my friends AR has what feels to be about half the recoil that my M4gery has (RR parts, Stag lower). But damn, the gas tube roll pin went in hard!!