I'm a believer in using a magnum primer when using moderate to large amounts of powder (especially ball powders) all the time.

This includes the .257 Roberts and larger.

Hornetfan



My 280 Ackley also prefers H4831 SC and Federal Match Primers. You didn't say what bullet you were shooting with that 61.5 grain load but it could well be that it is too hot which means poor grouping. I doubt if Magnum primers would make any difference but be warned, if you go to Federal 215M cut your loads back at least 2 - 3 grains to start. Those primers are just about the hottest LR primers made.

My 280 Imp loves H4831SC, groups are excellent. It also shoots RL19, RL22, and IMR 4350 well too, but I settled on the H4831SC. Velocities are slightly less but groups are very consistent and still around 3100fps with 140gr. I have tried mag primers in the past and did not notice any difference or improvements in my groups. A mag primer shouldn't be needed to ignite 60 grains of powder anyway, but it made no difference in my gun's performance.

I am fireforming with H4831. Groups are incredible, better than most of my varmit rigs. The load I am using is 53gr Norma brass and FED210M primer. Things really start opening up when I get up to 61.5grians which is about safe max. I am getting some flyers. I neck size only, bullet tension is the same everytime, measured at .004. RL22 is hated by this gun, I could not stay under 1.5inches with 3 shots. I was wondering if a Magnum primer would work better and give a more consistant ignition and tighten things up a bit. The gun is a 25 inch fluted Lilja on a blue printed Rem700 in an HS stock. 1.5lb blue printed factory trigger