CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.
When I started handloading in 1999 it was 308 and then 9mm.
With the 9mm I was interested in seeing how powerful I could make it.
I worked up until the gun blew up.
Between 1980 and 1999 I had been designing power supplies that I overloaded and blew up to find the weak spots. Then I would fix the weak part of the design and overload higher. This was like dynamite fishing. My competition was slowly producing unreliable designs, while I could produce reliable designs quickly.
When a power supply blows up, it is often like an M80 in the environmental chamber oven, or on the workbench it blows a hole in the ceiling.
But when a 9mm blows up the extractor shears off and goes to the right at lethal velocities, while the bottom of the magazine blows out the mag well with the ammo, magazine spring, and follower. The bits of brass can come back through the slots in the slide and hit the shooter in the face. The blood on his face is called "major face" from all the guys who tried to make the majors [bullet weight times velocity = 180 or greater].
Wanting to avoid all that drama, in a load work up, if a guppie belly case bulge appears on the case as the result of not being supported over the feed ramp of the barrel... this is precursor to lots of trouble. If one sees a case bulge in a workup, the workup should be terminated. A useful load would have to have less powder than caused the bulge. The amount less is called the safety margin.
Most 9mm barrels have a feed ramp intrusion of~ 0.19". The web of a 9mm brass case is ~0.16". This leaves 0.03" of thin case wall unsupported. That is where guppie bellies are made.
Back in 1999-2000 I tried working up all 9mm bullet and powder combinations to destruction. Most combinations cannot get enough pressure before no more powder will fit. The powders that will make trouble have a high [speed]x[density] product. They are also peaky, meaning big changes in pressure with small changes in powder. Ones to watch out for are; AA#5, HS-6, and 3N37. While Blue Dot may seem horribly peaky in other more voluminous cartridges, it lacks the speed-density product for 9mm trouble.
My favorite 9mm powder is Power Pistol, has a high speed density product, but it is anything by peaky. It blows a big fireball of unburned powder out the muzzle where it burns to make light.
Another thing that causes a pressure spike in 9mm is cartridges that are a tight fit in the chamber. Resizing loaded ammo so it drops in and out of the chamber freely can increase the threshold of case bulge by many grains of powder.
I have not gone back to 9mm experimentation since 2000, but what I learned was later applicable to experimenting with 25acp, 32acp, 7.62x25mm, 380, 9x23, 40sw, 10mm, and 45acp.
