magnum primers for 7mm mag

[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.