Is a mag primer needed with 7977? Thanks.

That depends on what you are loading it for. If I was loading a case larger then an '06 I'd try a magnum primer.

I'm looking in the Hodgdon 2015 Annual Manual (Magazine) and it has a long writeup on the new Enduron powders. And test load data is given for all three of the newer powders. And the laws of physics haven't changed with slow burning powers and large cases. In the IMR 7977 test data the standard calibers for the test are using CCI 200 primers and the magnum calibers are using Fed 215 primers.

Do you remember the 1966 hit song by the Doors "Light my Fire"?
It sounds the same now as it did back then, and nothings changed. (except all my vinyl records are scratched)

The real question is what is a magnum primer.

I've only used 7977 in maybe half a dozen rounds from the .243 Winchester to a couple of .30-06 length belted magnums, but so far it doesn't seem all that primer sensitive. This is true of many extruded powders, which tend to be less primer-sensitive than sphericals. But I also haven't shot it across as wide a variety of temperatures as I prefer before coming to any conclusions.

Have done all shooting so far in "normal" to 90-degree conditions so far, but am waiting for fall to test it in temps around zero, as in my experience powders (and primers) don't act the same when only the ammo is chilled and not the entire rifle.

But I can say that so far 7977 seems to be a very good addition to the powders in the H4831/RL-22 to Magnum/H1000/7828 range.

MD,

You hit on my exact concern, how will it perform with large charges in Wyoming/Montana Elk season condition.