I recently upgraded my Bushmaster Patrolman M4 to an Osprey Defense Gas Piston with a FailZero coating. I had some problems with it chambering rounds before, probably due to the ammo I was using and just wanted to upgrade to a piston to see if that would help. I'm still in the "trying it out" phase. After installing it I had to send my upper to Osprey to check out since it was firing but not chambering the next round. They fixed it and it was due to something with the pin hole in the front sight mount. I just got it back and just need to take it to the range but they said they put about 100 rounds through it and it was running like a sewing machine.
I want to add that I think Osprey customer service is TOP NOTCH. Joseph Scimeca tried to resolve the issue over the phone with me but then just said to send it in and they'll take a look at it for free. All it cost me was freight there and they paid for it to get back to me. I can't wait to get out and shoot it.