223 IS as effective as 308, at what MATTERS, and with a can, it's FAR better than 308. A 308 can that really IS effective at suppressing rapidfire, full charge ammo is SO big and heavy that it RUINS the rifle for anything but bipod type work. That is a FACT. The lw, compact 308 cans are pretty worthless with full charge ammo, in rapidfire. They are intended for SLOWFIRE, with 200 gr loads at 1000 fps. Hell yes, I can build a small, lw can for such loads. It's basically just a .45 ACP. 8" of 1.5" can will suppress such 308 loads to BB gun "noise", with ease, as long as you don't fire faster than 1 shot per second or so.