9mm with SMPP and Power Pistol

[ghbucky]

I've run out of SPP, but I do have SMPP

I'm using Power Pistol powder under a powder coated 125gr Lead conical nose bullet (Missouri Bullet).

Lyman Cast Bullet handbook shows 5.0gr - 5.5gr as the charge range (with standard SPP, of course).

I did a workup starting at 4.5gr. at 4.7gr there was pronounced primer flattening, but even 4.5 was pretty energetic.

So, I dropped it down to 4.3 and tried that. The slide locked back, so it seems good. I still think the primer is flattening, but I'm wondering if that is simply because the energetic ignition of the magnum primer is flattening itself on the breech face?

Should I keep testing lower charges to find the lower limit where the gun won't run?

[Unclenick]

If you are not seeing any other symptoms, you are probably OK. Primers flatten because they back out of the pocket and hit the breech face before the head can come back and reseat them. Flat, by itself is not an issue. But mushrooming, where the head first expands and then is flattened, is a problem. The symptom is the primers (decap one and check) head gets wider at the bottom of the cup than the sides are.

One test you can make is to see if it flattens when you don't have any backup space. Take the barrel out of the gun and load a few rounds with the bullet sticking way out so that when you drop a round in, it is level with the back end of the barrel. These may not feed well, but if you load them singly, does the flattening stop? The practice puts the bullet into the lands of the rifling, which tends to make start pressure consistent and often produces the best accuracy and least amount of leading. If it will feed in your gun, you may want to go to it for regular use (I do with target loads).

[ghbucky]

But mushrooming, where the head first expands and then is flattened, is a problem. The symptom is the primers (decap one and check) head gets wider at the bottom of the cup than the sides are.

Thanks for the tip. Yeah, I'm GTG at 4.5.

4.7 had a mushroom.