I use H414 on all my larger varmint cartridges (220 swift, 22-250 AI, 22-243, 243 AI) because it meters so well, and gives good accuracy and velocity.
From experience, and all I've read, standard primers are satisfactory for this powder in these size cases; but magnum primers are certainly reasonable, and often recommended for slower ball powders like H414.
When switching from standard to magnum primers, you need to check accuracy differences, which relate to velocity variations and uniformity, and you need a chronograph that...but all that fuss is part of the fun of safe handloading. :)