My brother has an old Rem M600 Mowhawk in 6mm, 18.5" barrel. He has had outstanding success on mule deer with Rem 100 gr Corelock factory loads. So goodthat he does not reload for it. Bullet expansion is dependable and so far so good. We have cronographed the loads at 2875 fps from that 18.5" barrel.
His twin daughters love the 6mm. Both have shot some nice bucks with it. The post mortum examinations have always left a very favorable impression upon him. He has never been disappointed.
Myself, I use a 100gr Sierra BT at 3020 fps in my Ruger #1 which is chambered in 6mm Rem too. I use H4831SC, CCI 200's, and Rem Brass.

Don