The decap/resizing die was set too high. About the thickness of the paper clip retainer at the first station too high. Rookie mistake. When you mentioned the bulge at the base that's where the case was hanging up both in the barrel and the case gauge. I realized I was fixing the wrong end of the reload.
► Here's the correct way to set "straight wall" pistol dies....
You want to "size" as much of the case as possible, but you do not want to fracture the incredibly fragile carbide insert by forcing the die it into the Shell Plate. With no case in the press, run the die down until it touches a piece of printer paper, and lock it there. On a Dillon this setting will slightly raise the Tool Head at the top of the stroke, but the paper clearance it will never allow the die to bottom out on the Shell Plate.
When I set up the 550 I checked for plunking and all was good. It seems, even with the incorrect setting on the resizing die, some of these would plunk and some not. Haven't figured that part out yet. Although I have never owned a case gauge until I started having 9mm plunking problems I think the money for the case gauge was well spent.
► Yes, the first half of auto-pistol cartridge "plunking" evolves getting the case all the way into the chamber. That is a Sizing Die setting. But the other half of cartridge "plunking" evolves getting the bullet into the chamber without burring it in the rifling. This is a Seating Die setting.
► Notice that the
cartridge gauge has no rifling, so the only way to check these clearances is to use the
barrel as your cartridge gauge. The correct auto-pistol OAL should be short enough to keep the bullet out of the rifling, but at the same time be long enough to feed correctly. You can easily check the "short enough" part of this with a "
plunk and spin test". A cartridge should: 1. fall all the way into the chamber using only its own weight. 2. Spin freely as it head spaces. And 3. fall back out using only its own weight. (No shaking, pounding, or hammering with the hands to "help".)
► Note here also that the auto-pistol rifling begins in each gun maker's barrel at a location that is totally
unique (like no other, individual, discrete) to that brand and model gun. So it is very likely that your PCR chamber is very generous, whereas your 1911 chamber may have much tighter tolerances. To further complicate matters, each bullet ogive shape is also
unique. (You discovered this when the
Gold Dot would plunk but the plated bullet would not.) So every time you order a new-to-you bullet brand, type or shape, you must go through this exercise all over again.
The bullet-to-barrel fit determines a lot of what we do in auto-pistol reloading.
These are much better quality rounds now.
Very glad things are looking better for you. Shoot safely, my friend.