I don't have a current Sierra manual, but Alliant shows 4.4gr MAX Bullseye for a 124gr Speer GDHP, as does the Speer manual. Hornady also shows 4.4 MAX Bullseye for their 124gr jacketed bullets, and Lyman's 48th shows 4.5. I think you are over max, and need to back off considerably.
Just a Shooter