iamdb, nothing personal against case gauges because they are useful for quick measurements, or when loading for multiple pistols where your handloads that get "passed" by the case gauge will work in the pistols with the tightest chamber dimensions.
Ultimately, the best case gauge you can get is the chamber in YOUR pistols barrel. If you only want to do a single handload for multiple pistols, load for the pistol that has the tightest/shortest chamber. For best accuracy, load specifically for the bullet you're using and the pistol it's to be fired from.
I realize that RCBS states that you can seat and crimp in a single operation, but what you're gonna find is a greater variation in OACL. To get the best uniformity, you really need to seat and crimp in 2 seperate operations. Maybe not so much a consideration for blasting ammo, but if accuracy is what you're after . . .
I've used dies from all of the major manufacturers and have found only one brand that will consistently seat and crimp with uniform OACLs and those are REDDING Titanium Carbide die sets. I used to never seat and crimp in a single operation because LEE, Lyman and RCBS dies just weren't capable of giving uniform OACLs. With a bullet like the Rem. 124 gr. JHP (old style) where I load my defense rounds on a REDDING boss single-stage press, I can maintain an OACL tolerance of +/- .002". What variation there is is likely from the bullets ogive variations.
And a word of caution about the LEE FCD. In cases where case-wall thicknesses vary and they do regardless of brand, or where bullet diameters vary, you can end up with a condition where the case-mouth diameter is above the SAAMI Spec for MAX. Like everything else, somethings gotta give for that cartridge to pass through the FCD. In some cases it can result in bullets being resized to a smaller diameter. Not a good thing and particularly not when using cast lead bullets that can get sized down to actual groove diameter or less where leading will result. My .45 ACP defense loads are a bit different because I keep my REDDING die setup to go with cast lead bullets and little to no crimp. Just enough to remove any flare, in other words. So my JHP defense loads get taper crimped seperately in a dedicated REDDING taper crimp die that does exactly what it's supposed to do and the real taper is only on about the top 2mm's of the case-mouth.
