rockytop

the other thread about primers for the 25-06 got my curiosity up. I been reloading about 4 years. I reload for 7mm mag and I' ve always used the winchester large rifle primers. I shoot the H4831 at 68.5 grains and a nosler bt 140 grain. I shoot one inch groups at a hundred. However, I sometimes I have one stray a little and I always figured it was me. My question, should I be shooting the magnum primers and what kind? If I change, I' ll need to drop my powder back and work my load up again. Also, where will I see the difference between the magnum and large rifle primers, i.e., speed, accuracy etc.

Vapodog

From the extremely little testing I' ve done with magnum primers and standard large rifle primers, I can say that in one instance I saw improved accuracy with the magnum primer using H-414 in a 6MM cartridge.....in truth I' m not convinced there' s any difference in large rifle primers and magnum primers at all.

oldelkhunter

There is a reason that the primer type is listed in most Reloading manuals...My belief and that of others is that once you cross the line from 270/280 case capacity your better off with a magnum primer because they should provide a more consistent powder ignition. With hard to light off powder in very cold weather they will also be helpful. When I was handloading my 280 I almost switched to Federal 215M because I knew the conditions of the hunt warranted it. I decided to keep the 210 m and it all worked out.. I have never used anything other than magnum primers in magnum cases including the 300 wsm and ever had a problem with velocity figures whether extremely hot or very cold.

RedAllison

Rockytop you got my curiosity up so I went and dug my old 7mag reloadin data out. First my Nosler reloading manual is the old No. 3 edition (updated printing 03/92). According to their info their 7Rem Mag data was developed with a Wiseman test barrel that was 23.5" , 1-9 twist rate and ironically they did NOT use magnum primers (Fed 215). Magnum primers typically are equivalent to an extra 1-1.5 grains of powder in standard calibers, but I doubt it would add that much in a large case like the 7mag, it would also depend on just how slow the powder you were using is.

140 Ballistic Tip: MAX. 66.0 IMR 4831, 3220 fps muzzle velocity and a 84% Load Density. (Your H4831 is a tad slower burning than either the IMR 4831 or my RL19 btw! Its practically the same rate as MRP and RL22.) I dont see why you wouldnt gain from a mag primer, but then again its probably not wise to exceed whatever your manuals say.

Now my own reloads were for the exact same bullet but I used RL 19 powder. 65.0 grains, 3333fps (adjusted for a 24" barrel) 84% Load Density. I am not sure as its been several years since I did those but I believe I also used Mag primers and shot that load as many times above freezing as below. I also had several cases that I blew the throat out of and those cases were first time reloads as well. When I ejected them the throat was GONE, just a case and neck. I even remember 1 or 2 that even blew the necks off as well. NOT comforting in the least!!! But they grouped well and tho they performed like glass bullets on deer, they killed like lightning. I also think my particular rifle a Ruger M77 7 Rem Mag, had a larger than standard chamber from the factory. Even when firing brand new factory ammo the spent cases would show a bright ring above the belt aka " incipient head separation" that has probably caused me to basically quit shooting the rifle much anymore. LOL sounds like all the reason I need to have a 257 WBY Mag made from it!!!

Hope this helps,
RA

handloader1

Bullet manufactors spend a great deal of money generating load data right down to what primer to use. Good luck.