My day job involves working on computers... I wish it was something glamorous like "International Spy", but it isn't. In the world of computers, we have a term called "PEBCAK" (alternate spelling is PEBKAC -- either works)... Stands for:
And that turns out to be the problem here... the problem is with the guy pulling the trigger...
I took the *exact* same ammo (along with some additional test ammo) to the range today and absolutely *everything* fired flawlessly. FCD, no FCD, short OAL, long OAL, factory --didn't matter. It all fed and fired.
What was the difference? Before going to the range today, *I* cleaned the firearm.
Yep -- I made the stupid, STUPID
mistake of trusting the previous owner's cleaning. The firearm looked immaculate and seemed to cycle and work flawlessly. However, whatever he had used was apparently too sticky -- or had become too sticky while the gun sat unused. Residue, etc, stuck EVERYWHERE and gummed up the works. The undersized Aguila's were still working, but I'm betting that had I continued to shoot yesterday, they would have eventually failed as well. This also explains why a recipe that was working early in the session yesterday stopped working.
When I cleaned it last night, I couldn't believe how much dirty stuff came out of the firearm -- and that is how the "cleanliness" theory (one of the theories I mentioned in the original post) got started. Even though I shot more rounds today than yesterday, my firearm is visibly cleaner in and around the chamber/feed ramp than yesterday. The slide felt snappier today as well -- amazing what a significant reduction of friction will accomplish.
To make matters worse... I know better.
I've seen problems similar to this cause malfunctions in other peoples' firearms. I've even seen grease-turned-glue cause problems for electromechanical devices. I had to completely disassemble and clean a high-end tape deck that simply wouldn't engage because the "lubricant" had turned so sticky it had basically glued surfaces together.
So -- now I can get on with the task of finding which combination of bullet/powder produces the best result in each firearm, etc. and reduce my recipe-count to a smaller number.
I'm sharing this not only to reinforce my status as today's idiot-of-the-day, but as a reminder to not forget the basics. This was relatively minor and not an oversight in the reloading process - thankfully. Nothing happened, and the only injury is to my pride...