loading for 9MM semi auto

Found out something very interesting that many members may already be aware of. I spent some time at the range last week with my P938 9MM and had previously loaded up some "target" loads with ball 124 grain bullets. When I started shooting I began to run into problems with feeding including double feeds. First thing that went through my mind was magazine, then ejector. I backed off for a minute and then realized although my reloading manual stated that my loads were safe I realized that for my gun the loads were not powerful enough to reliably function the slide. I switched over to some factory loads I had also brought and functioning returned to 100 percent. I then made up more reloads with a charge roughly one half grain under max and functioning was perfect. The recoil spring in my 938 is a bear and I can see why lower powered loads would not function reliably. I also contacted Sig Sauer and when speaking with one of their Techs was told basically the same thing as I had found out. Very interesting the little things that you sometimes overlook.

Not just 9mm's, but semi-autos in general.

The cartridge needs enough "oomph" to make the gun work.

With a .38 revolver, a guy can get away with some real pipsqueak loads because it just doesn't matter. The revolver will fire them just fine and the power of the cartridge is not used in any way to operate the gun. With a semi-auto though... Have to keep enough suds on tap to work the thing.

Lighter loads can often be accommodated with a lighter recoil spring too.

Guy

It seems to me that the smaller, compact autos always take more "oomph" to cycle. My Beretta and Glock will cycle 124gr bullets with 3.0gr of IMR700X. If my memory is correct, my little Kahr CM9 needs over 4.0gr to cycle.

It has to do with the spring stiffness as to how much oomph you need to function a pistol.
Back when I was shooting bullseye with my 1911 45 ACP I would use a very light poundage spring and with 3 grs bullseye and a 200 gr lead SWC it was a tack driver and it functioned perfectly. It function slow but perfect. It was almost like BANG then you could hear the action go clack clack in the function.