If its the WSSM A-bolt its a Super Short action. Only short cartriges will fit. Factory the largest would be 25 wssm, but the 6.5 Heaton is an option also there are two other wildcats I've heard/seen. The 30 WSSM(its called something else, used in ARs' some). Also, a place in Indiana has the 358 WSSM magnum that is legal in that state for deer hunting.
I never thought of single feeding as above was mentioned, I'd probably go with the SAUM as its a little shorter than the WSM and may not have to pull bolt to load.
Let us know what you go with, I have a 25 wssm in an A-bolt. Nice light rifle, but barrel leaves a little to be desired.