All of the military m249 para barrels I've seen are the 9/16-24LH threads... that said I think that some of the factory M249s para guns were coming with a para barrel that was actually threaded to 1/2-28RH threads. Let's say you can get a can on it though, all the para barrels have the newer non adjustable gas block. It's going to be way WAY over gassed with the can. You're better off finding an older m249 barrel with the adjustable gas, chopping it to whatever length you want and threading it to 1/2-28. They also have a set screw screwed into the bottom that you can adjust gas port size with. The setup I use is a 20" adjustable gas block barrel cut to 14", then I added a third bleed port to the gas collar (notched the gasblock for it too) now I have a gun that will run about 850- 900 ish on high gas no can, 650 ish on normal gas no can, and about 650 on low gas with a can. OR the other 3 setups that aren't ever used would be, it won't cycle on low gas with no can, about 900+ on mid gas with a can, and I haven't tried it on high gas with a can, but assuming shit doesn't start flying off, I'm guessing it would be 1200+. This is all on a post sample mk46, but I can tell you that putting a can on a saw will absolutely speed them way up.