Have had 3 factory Mk V s (german P code, japan H code and USA S code) in 300 from early 1980s to present. They all liked RL22, MRP and RL 25 (depending on bullet weight) w/ neck sized Wby or Nosler brass, Fed 215 or WLRM primers, Hornady bullets. 7828 didnt produce consistently for me with that brass/primer combo in my rifles. Always keep at least 1 jug of the 3 powders on hand.