Looking to suppress. Anyone know the thread pattern?

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.

Just FYI the muzzle device on the stock para barrel is welded on to meet length requirements.

Also, be very, very careful suppressing a M249. It's less an issue on semi, but slapping any old can on a belt gun without doing kinematics is asking to break things. The gas port is sized for reliability across a wide variety of operating conditions. This typically means under good conditions the gun will run overgassed, especially when using a box magazine as you have no belt pull requirements, in order to ensure that it will cycle reliably and have enough belt pull when its cold and the gun is full of crud. This was less of an issue back when you  had multiple gas settings like on the early M249 and Minimi as it allowed you to have a adverse setting with a larger port size. But DOD in their infinite wisdom decided it was a liability to be deleted to prevent soldiers from cranking the gas up to increase ROF rather than training them on the dangers of doing so. As such and as M249S is designed to be semi version of the issued SAW, you can quickly run into early unlocking, heat retention, timing issues, etc. if you slap a high back pressure can on there and have no means to check let alone compensate for the even greater port pressures your're now dealing with.

Good post.

We ran some cans on some of our saw and those things were like damn buzz saws. Not saying you can but I’d really choose wisely on what can you run