Was recommended that I post this here as I might get more help with my issue.
So I bought a full size USP9 as a can host. Not the SD model, just a base model and threw a factory threaded barrel in it.
Will not cycle with the can on and running 147gr subs. As in the slide doesn't cycle at all, just a single shot at the moment. Now if I take the can off it cycles the subs perfectly, so it's not an ammo problem I wouldn't think.
I did not try to run supers through the can, I'm following up and trying that on Friday.
Can is a Osprey 40 can running a 9mm piston.
Some have said throw the SD recoil spring assembly in it as it is beefed up for suppressor work, but I don't see a beefier spring setup helping the fact that it is not cycling at all. I could see if it was cycling too fast due to the extra pressure, but that isn't the case. Also I hate to throw another $100 at this rig if it just isn't going to run, already deep in it with the price of the gun, sights, barrel and extra mags.