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2/14/2010 6:10:46 AM EDT
2/20/10
Received the new piston yesterday (Feb 19) and headed off to the range this morning.  Weather wasn't great, but didn't want to wait another weekend before finding out if my short stroking problem was fixed or not.  The good news is the new piston functioned flawlessly.  Not one failure to fire or feed after 300 rounds (Privi 55GR) once again using a variety of magazines.  Started off with the ones (C Products) that consistently single shot last weekend, but didn't experience a single hiccup.  Must admit before squeezing off the first round, I was mentally preparing myself that I was going to have to send the upper to Osprey for them to check out.  Glad I was wrong!!! Plan on converting my other AR in the near future.  

2/13/10
Finally made it to the range yesterday after my December install.  Temperature was in the low 30's with a slight breeze.  Expectations were high I would only experience a few minor break in problems similar to other range reports.  Unfortunately this was not the case.  After nearly 300 rounds using Privi 55 grain, it was one short stroke after another, using a variety of magazines (CMMG, USGI, C Products). The upper is a DTI 16" HBAR with an Armalite lower. The BCG was properly lubed (CLP) so I felt reasonably confident this was not part of the problem. The bolt also failed to lock back consistently on the last round.

When I arrived home, I called Cory at Osprey, and said it looked like I needed to send my upper in for them to take a look at.  He said that wouldn't be necessary as they are familiar with the cycling problem involving some early production pistons being slightly out of spec. Said he would send me the new piston which would correct the problem and I should have it by the end of next week (Feb 18).  Crossing my fingers this will correct the problem.
2/14/2010 6:32:35 AM EDT
[#1]
Are you using a heavy buffer?

I have seen piston problems when using heavier buffers. Most of the time you only need a standard buffer.
2/14/2010 6:45:29 AM EDT
[#2]
Heavy buffer...
2/14/2010 7:53:12 AM EDT
[#3]
Quoted:
Heavy buffer...


I have an "H" anti-tilt buffer and it runs fine. Doubt it's the buffer; likely the out-of-spec piston chamber like they said.

2/14/2010 9:07:15 AM EDT
[#4]
I had the same issue unfortunately.  Got a new piston (slightly larger I believe), and it's running perfect now.  I'm using a H-buffer BTW.
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