Sorry for the delay but been a bit busy, I've built up this to give you and Idea.
Original 45 degree Bud Orr Sniper.
Pump stop Barrel (finishes flush with the pump end)
MPM Bottomline
Expamsion chamber
Slamfire kit
Lapco 45 grips (original grips aren't great for slamfire)
The bottomline setup is good for air or CO2.
It's a good speedball slam fire setup.
Is this the kind of thing you are after?