Just put together an 11 bore rifle on a Mk111 Greener police gun. My "rifle" barrel was cut by Clearwater reboring (Jim Dubell) and has .728" bore, .744" groove, and 80" twist. Yes, I just had the shotgun barrel rifled. It has Brit proof for 1 1/2oz nitro, so feel it will do fine with round ball loads around 1200 fps. The Mk111 has the "funny" chamber and firing pin requiring modification. I cut my chamber at 2 1/2" since the R/B won't need a lot of space in the case. Also cut a short "forcing cone", but may change chamber length and/or throat according to how it shoots. Another issue that may be troublesome is the rim recess cut for the 12/14 chamber is quite generous and results in lots of headspace for a standard 12g hull. If necessary I can set the barrel back a thread, but that will require forend mods. My "rifle" is unchanged externally, full forend and mil buttstock. I'm awaiting arrival of the R/B mould so have yet to shoot. Will be great fun!

Otto