Effect of primer change

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pacobillie

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I am loading 200 grain Nosler Accubond bullets in 300 H&H magnum. My accuracy load was 69.5 grains of IMR 7828SSC, with a Winchester LRM primer in WW Super brass. COAL is 3.6 inches. No signs of excess pressure. Average velocity for three shots was 2831 fps (2843, 2841 and 2810). All charges were weighted to within a tenth of a grain.

I tried Federal LRM match primers, and the velocities became more consistent, but also a bit higher and the group opened up from about 1 to 2 inches. The switch to Federal magnum match primers is because some previous slightly hot loads had expanded the primer pockets on some casings. Federal primers are slightly bigger than their Winchester counterparts and addressed the loose primer pocket issue.. As you know, 300H&H brass is hard to come by and quite expensive. Hence, my efforts to save the brass.

I am now getting an average velocity of 2865 fps with that load. So, the Fed primers appear to be quite a bit hotter. Other than the groups opening up, there are no signs of excess pressure. How much would you back off on the powder charge?
 
Federal primers are a hotter primer. I experienced this recently with my 32-20.
93 gr. cast with 4.6 grs of Unique. 100 rounds total. 60 with Winchester sp and 40 with federal sp. For use in a rifle the loads where nowhere near max so I wasn't worried about over pressure. Both loads where safe but I noticed an increase in noise and recoil. i had experienced increases before put not this noticeable on a low load. Velocity was increased by 90 fps. The load with Fed primer I have since increased to a max load for my rifle. I backed the charge weight down after primers where flattening to much.
 
pacobillie said:
I am loading 200 grain Nosler Accubond bullets in 300 H&H magnum. My accuracy load was 69.5 grains of IMR 7828SSC, with a Winchester LRM primer in WW Super brass. COAL is 3.6 inches. No signs of excess pressure. Average velocity for three shots was 2831 fps (2843, 2841 and 2810). All charges were weighted to within a tenth of a grain.

I tried Federal LRM match primers, and the velocities became more consistent, but also a bit higher and the group opened up from about 1 to 2 inches. The switch to Federal magnum match primers is because some previous slightly hot loads had expanded the primer pockets on some casings. Federal primers are slightly bigger than their Winchester counterparts and addressed the loose primer pocket issue.. As you know, 300H&H brass is hard to come by and quite expensive. Hence, my efforts to save the brass.

I am now getting an average velocity of 2865 fps with that load. So, the Fed primers appear to be quite a bit hotter. Other than the groups opening up, there are no signs of excess pressure. How much would you back off on the powder charge?
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This is very interesting information. I have a stock of Winchester LR primers and a stock of Premium Gold Medal Large Rifle Match Primers. I will do a similar experiment to yours this summer. I will finalize a load that I am happy with and test its accuracy, then I will switch primers in a follow up load and test accuracy ... and see if there is a big difference.
 
My own limited experience, Feeral Primers run hotter than the S&B Primers I was using last season. Fed 210 GM, running5-23 fps faster in my .260 Remington... ymmv, fwiw
 
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