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Rimfire5 · January 24, 2013, 08:58 AM

I have experimented with LR and magnum primers with my .270 and .30-06 loads on the assumption that a magnum primer would ignite the powder column a bit more vigorously.

In both calibers, the accuracy was slightly better with the magnum primers and the point of impact is slightly different (1/4-3/8ths inch at 8 o'clock at 100 yards with the .270) with the magnum primers.
The average group size was tighter with the magnum primers (0.860 for the LR primers versus 0.761 for the magnum primers with the .270 using 140 grain Nosler BTs with 54.8 grains of IMR 4350 at depth 3.370). That is .020 off the rifling in my .270 with the 140 Nosler BTs.

My chronograph measured velocity with the magnum primers and the same load with the magnum primers was about 12 fps faster on average with the .30-06. SD was almost identical.
I didn't chronograph the .270s (didn't set it up that day).
I didn't notice any appreciable difference in recoil with either caliber.

I have more testing to do with a variety of loads but these results were interesting.

January 24, 2013, 08:58 AM	#10
Rimfire5 Senior Member Join Date: January 2, 2009 Location: Northern Virginia Posts: 922	I have experimented with LR and magnum primers with my .270 and .30-06 loads on the assumption that a magnum primer would ignite the powder column a bit more vigorously. In both calibers, the accuracy was slightly better with the magnum primers and the point of impact is slightly different (1/4-3/8ths inch at 8 o'clock at 100 yards with the .270) with the magnum primers. The average group size was tighter with the magnum primers (0.860 for the LR primers versus 0.761 for the magnum primers with the .270 using 140 grain Nosler BTs with 54.8 grains of IMR 4350 at depth 3.370). That is .020 off the rifling in my .270 with the 140 Nosler BTs. My chronograph measured velocity with the magnum primers and the same load with the magnum primers was about 12 fps faster on average with the .30-06. SD was almost identical. I didn't chronograph the .270s (didn't set it up that day). I didn't notice any appreciable difference in recoil with either caliber. I have more testing to do with a variety of loads but these results were interesting.