In the AR platform, the main brands that have a factory op rod piston SBR that I can think of are:
- H&K
- LWRC
- PWS
- Adams Arms
- LMT MRP series
- Colt P0923 and SCW0921P
- SIG516
I have had about about 890 rounds through my PWS MK110 Mod 1 upper (using the a lower with the Vltor A5 system), most of those suppressed with a Surefire SOCOM556-RC. No issues thus far, besides some user induced malfunctions (forgetting to change the gas block from the suppressed setting to unsuppressed after taking off the suppressor). Most reviews have been positive, and the long stroke design supposedly is more balanced than the typical short stroke ARs. It's a fair bit cheaper and lighter than LWRC (PWS recently had a price bump in MSRP, but you can still find them for good prices online), comes with Keymod rails, and has an adjustable gas block (4 position; in theory, it can be changed with just a bullet, but I prefer using the supplied tool or a screwdriver or whatever, as the bullet doesn't have enough leverage, IMO).
The caveat to all this is that I have very little long arm experience, as I have had only 8 hours of formal training (CSAT), versus over 100 hours in handgunning. I picked PWS based on the strength of it's paper specs (a piston was desirable because it was going to be a suppressed shorty) and the mostly positive feedback from various forums. It's done well so far, but obviously 890 rounds is pretty damn minimal.
