I'm running a Shooter Design (SD) threaded barrel on it. I don't recommend any steel barrel if you're running an aluminum slide on your Glock. Because of the floating design of the outer barrel, a steel barrel will just shave bits off the aluminum slide till there's none left.. LOL.
And also on the topic of the free floating barrel, I've noticed that running the SD barrel on my HK3P (WE) glock is looser than running it on a Tokyo Marui Glock. This is the main cause of cycle failure. So in short, the Osprey functions flawlessly on a TM but you may encounter some cycling issues on a WE/HK3P using this set up.
Here's my Marui Salient with the Osprey:
I also bought one of the GM RMR slides, but haven't yet had time to install it to test it out. Will let you guys know how it runs with the SD threaded barrel when I do get around to it.