#1 Goal of loading for a semi-auto is: Will it reliably cycle the action?
After using the disassembled barrel for the plunk test, I did NOT hand-cycle the gun.
I believe you should have. If not hand-cycling then firing the rounds in a gun. You did. You had problems. Ergo you did something different and wrong and got unreliable ammo.
1) because I was using info from previous loadings using that OAL and
Well, something went wrong, didn't it.
2) any cycling of live ammo is not something I like doing if I don't have to.
When I carry a firearm at work, I cycle one round into and out of the chamber every shift, loading and unloading. I know for a fact that ammo that ammo goes through that pistol.
The rounds loaded previously shot fine.
Obviously, something was different, you did it, and you need to identify it and remediate the issue. No one else can do that for you. It is your process, and your result. You own it.
I was just clearing out the last 50 rds of the Ranier 200gr plated RN bullets I had on hand.
Whatever you did, something didn't work right.
Why some (3) fired and the rest jammed is a mystery.
I am certain that something you did caused this, and it is not good. No mystery there.
I randomly checked OAL on the rounds after setting the initial length. They were OK. Two days later - they weren't. I think I am gonna set my OAL about 0.010" less in the future and see how that affects them.
I don't think you get it. Your cartridges did not change. How you measure different things, on different days, consult references, and interpret results may be introducing unintended and undesired variability in your results. Pass the plunk test, but gun jams means you loaded bad ammo, and are not properly doing, or interpreting your plunk test. The plunk test will rule out over diameter ammo, but it is an incomplete test, because the gun is disassembled, and the cartridge is not: 1. going into the magazine, 2. coming out of the magazine, 3. going into the chamber, 4. action closes (in battery) with the round in the chamber, 5. is fired, and 6. finally gets ejected. That is six different "test" that happen every time you fire a cartridge. I recommend you determine what it was and remediate your methods.
I do recommend you get and properly use a micrometer, a case guage for you cartridge, and reread your manual (for that caliber) and review all data (COAL, case length, look at your marked barrel caliber), and, examine your brass condition and headstamps ) EVERY TIME you reload. Look closely at the top of this case gauge:
https://www.amazon.com/Lyman-Reloading-C-P-Pistol-Cartridge/dp/B005I0IU5E
notice the High-Low marks, when you plunk your round into the case gauge head-stamped part of the brass must be between these marks. The is the SAAMI specification. That is a much better measure and test than your barrel plunk test.
You can make dummy rounds to try different COAL's safely. If you know what you are doing and are careful, you can cycle live rounds safely, too. Quite a few people do that everyday.
