I use a 20" with Thunderbeast CB9, its mainly for prairie dogs. I added a Noveske switch block, but it really wasn't needed. I shoot most things suppressed now, still use hearing protection. On a semi-auto, the action noise can be quite noticeable even with subsonic loads.

Although I own an AAC M4-2000, I would point you towards the Ti suppressors if its just for hunting. The reduction in weight is very noticeable when swinging the gun on moving targets in the field. I picked up a TBAC Ultra 7 (9.9 ounces) for my 16" 6.8 SPC hunting build and its pretty amazing the improvement with handling.