[Theohazard]

The SDN-6 is the best all-around rifle can on the market, in my opinion. It's a super-durable full-auto-rated .308 can that's also very quiet on 5.56 (with less back pressure), and it's also optimized for .300 Blackout subsonic. I love mine. I only run it on 5.56 right now, but I'm starting a 300 Blackout build when I can afford it.

On thing about the 51-tooth QD mounting system: It's sometimes a little loose, but it's not an issue, and it won't back off at all unless something is damaged somehow. When you're attaching the can, it's a good idea to press down on the release tab while you screw it on; this prevents the ratchet lock on the can from "clicking" against the teeth on the mount. It's not 100% necessary to do this, but it doesn't hurt and may make the can's mounting system wear less after years of coming on and off the mount.

Also, I've discovered that some 51t mounts are tighter than others. Every time I mount a 51t muzzle device to a rifle, I try a bunch of mounts to see which one fits the best. For whatever reason, usually about 1 in 4 mounts is tighter than the rest.

EDIT: (Forgot to mention the threaded option.) The AAC Hunter is the threaded version of the SDN-6. AAC has been promising it for a year and a half, and it still hasn't hit the market yet. Supposedly, it's finally coming out in September, but I wouldn't hold my breath if I were you; I be surprised if it actually came out this year.

Thread-on cans are lighter and, in theory, slightly more accurate. But they take a lot longer to take on and off, and they require your host weapon to just have the bare threads showing. I don't recommend a thread-on can unless you're doing a pin-and-weld job, or if you don't plan on taking the can on and off very much, or if you plan to use it on multiple rifles.