I have scoped a number of FWB300's.

Main things to watch for is some older 300's have very short scope rails so can be awkward to mount with proper eye relief, later models with the longer rials are dead easy. The other thing to watch is the objective bell obstructing the loading port.

One of the compact scopes that can be picked up might assist with both of the above mentioned issues.

The 601 I think will be a trickier proposition.