View Full Version : Are magnum primers needed for AA#7 and AA#9?
Some loading data i see say mag primers are a must and i see lots of info that mag primers may just increase pressure more than do much of anything else. What is the consensus here on these two powders?
The use of magnum primers does increase peak pressures and velocities, but they should be used by us amateurs (without pressure-testing equipment) only if they were used by the testing organization. Substituting a magnum primer for a standard one could increase pressures to dangerous levels.
+1 I've never used mag primers for any powder in the 10 and from what I read they would only marginally boost velocity. If you choose to experiment with them, follow standard practice of starting with lite loads, increase a couple of tenths per batch of 10 rds, and look for pressure signs telling you to stop and back off.
Don't see why just standard large primers wouldn't be good enough for any 10mm load, since .40 S&W uses small primers just fine.
I have tested my hot #9 loads with both and didn't see enough difference to make it worth the cost difference.
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