Thanks Bill, that's exactly what I wanted to here. I will give them a call tomorrow. I knew someone on GTA would come through for me.
I've changed a couple of them. The M4-177 has a rifled barrel and swaps in perfectly. You will also need the plastic barrel support as they get broken getting them off the old barrel. Just call Crosman for the parts; barrels $8.24, supports $1.00.M4 Barrel# 417-005 ...Support# 760E-125