davkenrem
01-19-10, 23:23
I took my new AR out for the first time this Saturday and had some short stroking issues.
Saturday I fired 80 rounds. The first 40 seemed to fire fine, the last 40 began to short stroke. It started with about every third round and progressed to every round.
I fired three different brands of ammo. The first 40 was UMC 55gr, the next was ATI Tactical 62gr. Monday I tried a third brand of ammo American 55gr with the same results. I used two new 30 round Magpul PMags.
The gun would fire and eject every round but would fail to load the next round causing either a partial feed or no feed at all. All brass was landing at the 5:00 position.
Between Saturday and Monday I disassembled the gun and inspected the BCG and all looked normal. No excessive carbon build up, Gas rings were not lined up. I thoroughly cleaned it and relubed it with SLIP2000 and set aside. I inspected the upper and fully cleaned it and lubed it. Nothing looked out of place. I closely inspected the FSB, thinking it might be a gas hole alignment issue due to it needing to be removed to install the FF handguard. It looked properly installed and the guy who did the work is a trusted AR Smith. Reassembled and performed a function check and all seemed well.
The gun originally had a commercial buffer tube on it but was changed to a milspec buffer tube with a Magpul CTR MilSpec.
The lower was new, unfired bought from Adco. The upper was purchase used from the Equip. Exchange on AR15.com. I had the new Midwest HG installed after purchase.
Outside temp was in the 20's.
Build Specs as follows
Rock River Arms Lower w/ Mil-Spec Trigger
Mil-Spec Buffer Tube
MagPul CTR Mil- Spec Butt Stock
Standard Buffer Carbine and Spring
Used BCM Mid-Length Upper
Rock River Bolt Carrier Group
Midwest Industries MI-T9 Handguard
MagPul PMags 30rnd
Standard FSB and A2 flash hider
Several possibilities:
Lube is congealing in the cold weather.
Gas leak some where in the upper.
Improper buffer or spring.
Used upper, bought someone else's problem.
Just a note I'm not an AR newbie. I have owned at least 10 different AR's and was an Army 11B in the early 80's so I know how to clean and lube the system and keep it running. But this baffles me.
I had one other upper that acted this way. It was a Dissy built by Tony's Uppers and I could never get it to run.
I await your input.
Thanks in advance,
Saturday I fired 80 rounds. The first 40 seemed to fire fine, the last 40 began to short stroke. It started with about every third round and progressed to every round.
I fired three different brands of ammo. The first 40 was UMC 55gr, the next was ATI Tactical 62gr. Monday I tried a third brand of ammo American 55gr with the same results. I used two new 30 round Magpul PMags.
The gun would fire and eject every round but would fail to load the next round causing either a partial feed or no feed at all. All brass was landing at the 5:00 position.
Between Saturday and Monday I disassembled the gun and inspected the BCG and all looked normal. No excessive carbon build up, Gas rings were not lined up. I thoroughly cleaned it and relubed it with SLIP2000 and set aside. I inspected the upper and fully cleaned it and lubed it. Nothing looked out of place. I closely inspected the FSB, thinking it might be a gas hole alignment issue due to it needing to be removed to install the FF handguard. It looked properly installed and the guy who did the work is a trusted AR Smith. Reassembled and performed a function check and all seemed well.
The gun originally had a commercial buffer tube on it but was changed to a milspec buffer tube with a Magpul CTR MilSpec.
The lower was new, unfired bought from Adco. The upper was purchase used from the Equip. Exchange on AR15.com. I had the new Midwest HG installed after purchase.
Outside temp was in the 20's.
Build Specs as follows
Rock River Arms Lower w/ Mil-Spec Trigger
Mil-Spec Buffer Tube
MagPul CTR Mil- Spec Butt Stock
Standard Buffer Carbine and Spring
Used BCM Mid-Length Upper
Rock River Bolt Carrier Group
Midwest Industries MI-T9 Handguard
MagPul PMags 30rnd
Standard FSB and A2 flash hider
Several possibilities:
Lube is congealing in the cold weather.
Gas leak some where in the upper.
Improper buffer or spring.
Used upper, bought someone else's problem.
Just a note I'm not an AR newbie. I have owned at least 10 different AR's and was an Army 11B in the early 80's so I know how to clean and lube the system and keep it running. But this baffles me.
I had one other upper that acted this way. It was a Dissy built by Tony's Uppers and I could never get it to run.
I await your input.
Thanks in advance,