Northern:
Ruger reports a 1:20 twist rate. Yes, that will stabilize a 300 grn ball without overdoing it.
I can't speak to MFR bullet selection, I've no experience beyond 'hardcast'. The clip follows the SAAMI max OA length at 1.610". 300 grn ball will load, but the net case volume is reduced when OAL is kept within limits.
I'm interested in a 96/44 myself. - I'll follow your reports.
Cheers!