Large rifle or magnum large rifle primers

I have been reloading for a long time and always wonder what range do you switch to the mag primers. My 308 Norma mag I always use a mag prime with 75 gr 4831 sc. But now I am loading some 6.5x284 at 51 gr of 4831 sc and was wondering if I need to switch to the mag for that load? I know the mag does have more fire power and it would run the loads a touch higher.

After having some hangfires on a load, I decided the following.
Use magnum primmers for:
-Hard to ignite powder, usually slow/ball powders.
-When recipies call for 60+ gr.
-When loading below about 85% case capacity.
-Or if getting close to multiple of these conditions.

It is no fun to have a large cartridge in the chamber and hear a click. Especially if it could be followed by a delayed kaboom.

Thanks Adams that is what I was thinking around 60gr but I was not sure.