LP primer flattening

[Bill Steele]

I got a deal on a case of Federal Match Large Pistol Primers a while back.

I have been fooling around with some .44 Target loads lately and in one of my hotter loads (14.7 gr AA-#7, 240gr MBC LSWC, 1.6" OAL) and found the Federal Match primers seemed to want to flatten some.

The load is a "start" load in the .44 Rem Mag Accurate data. When I shot this load I was getting a little more pop than I had from previous target loads, but it wasn't anything really stout that would be normally associated with a full house .44 Magnum round.

The flattening was a mild mushroom on the primer case bottom. Normally I would associate this with the "getting pretty hot" pressure range, but everything in the load is pretty mild (i.e. powder load, OAL, mild roll crimp, etc.)

Has anyone else seen this with Federal Match primers?

[iareConfusE]

I don't use Federal match, but I do use regular federal large and small pistol primers. Federal has the softest primers cups of any primer manufacturer out there, so they're probably more prone to flattening than the others. My primers actually sometimes get flattened when I'm just priming a stiff case like a S&B.

[GeoffLinder]

+1 to Federal primer material being more ductile.

1. Is the primer flattening filling the primer pocket to the edges and completely removing the rounded part of the cup?

2. is the primer material flowing back into the firing pin hole around the firing pin indentation?

If either or both of these are happening then you do have an over-pressure situation. If neither is happening and the edges of the primer are still nicely rounded, then you most likely just have some Federal Flattening going on

[Bill Steele]

The primers are pretty flat in the case. The nice cupped look when they are seated is gone and they have that flat sequin bead look. The primer strike area looks fine, but the cup area is spread such that the primer has to curve back in at a fairly steep angle to get back to the cup cylinder. A little muffin top angle.

The load should be pretty light, I think I will load up a few with WLP primers and see how they look after shooting. If the WLP primers flatten, then I will be making some notes in my load data book about the Accurate #7 and my Model 29.

Thanks guys.