Per Alliant, do not use magnum primers with 2400. The "t" is a multiple in some cases
...didn't have to trim down to 1.280"...checked the brand new Starline cases which I used and they are already 1.280"![]()
No, you do not need a mag primer for 2400. Just that you made 2 changes to the recipe so it was not to a "t" It least not a capital T.

As mentioned in another thread,(and here) if the bullet seated to the crimp groove, I see no reason to go over it.? It was mentioned for the heavy bullets 170 or so that will not fit the cylinder.
However you do like to experiment with "stuff"
