I have a S&W 76 and I am very pleased with it. I am in my 3rd year of ownership.
-It is slightly on the hefty side with its heavy gauge steel tube, but with that it offers smooth full auto operation with little recoil
-It will eat any type of decent quality ammo , 115 gr 124gr, 147gr, have not tried 158gr subsonic
-rate of fire is robust but perfect in my mind
-it can get real dirty, and still function. It has special sand cuts in the inner tube surface
-accuracy is very good - I can punch the head out of silhouette targets at my local indoor range at 15 yards plus.
-parts are a scarcity but Richard at BWE is beginning to fill the void. I have bought a number of his spare parts so far.
-watch for trigger bar wear. This seems to be a long term / high use wear issue, but I have seen no replacement trigger bars anywhere
-extractors can wear rather fast, so always have a few in your inventory
-Nearly all of this applies to the MK760, but I'm not sure on the accuracy part, because I have read criticism on that in the past.