The drop in case gauges you use can vary in size, meaning diameter and headspace length.
Example below with .308 Winchester case gauges, below is a "FIRED" Lake City 7.62 case in a Dillon case gauge.
Below is the same Lake City 7.62 case in a JP Enterprise case gauge, and this gauge is closer to minimum SAAMI dimensions, meaning smaller in diameter.
I have different manufacture pistol gauges, in 9mm I have a Midway case gauge and a 7 hole EGW case gauge. And the EGW gauge is smaller in diameter.
Bottom line, I'm loading for 9mm that will be fired in Glocks and Sig pistols and all of them have chambers that can vary in size. And I know that any loaded cartridge that passes a plunk test in the EGW gauge because of its smaller diameter the loaded round will fit in any chamber. The Midway gauge is labeled "Max cartridge gauge" and basically only checks maximum case length and diameter.
Below a pistol case with a proper taper crimp.
Below a case without a proper taper crimp "BUT" could pass a plop test in larger diameter case gauges.
On top of this each type barrel will have a max OAL and OAL is always gun & bullet specific, regardless of the reloading data. And why your barrel is the best gauge for "double checking" loaded rounds against your pistol gauge.
And the Lee factory crimp die with a carbide ring in its base will size bulged crimps on the longer cases that you never trim and can hang up in your barrel.
Example below with .308 Winchester case gauges, below is a "FIRED" Lake City 7.62 case in a Dillon case gauge.

Below is the same Lake City 7.62 case in a JP Enterprise case gauge, and this gauge is closer to minimum SAAMI dimensions, meaning smaller in diameter.

I have different manufacture pistol gauges, in 9mm I have a Midway case gauge and a 7 hole EGW case gauge. And the EGW gauge is smaller in diameter.
Bottom line, I'm loading for 9mm that will be fired in Glocks and Sig pistols and all of them have chambers that can vary in size. And I know that any loaded cartridge that passes a plunk test in the EGW gauge because of its smaller diameter the loaded round will fit in any chamber. The Midway gauge is labeled "Max cartridge gauge" and basically only checks maximum case length and diameter.
Below a pistol case with a proper taper crimp.

Below a case without a proper taper crimp "BUT" could pass a plop test in larger diameter case gauges.

On top of this each type barrel will have a max OAL and OAL is always gun & bullet specific, regardless of the reloading data. And why your barrel is the best gauge for "double checking" loaded rounds against your pistol gauge.
And the Lee factory crimp die with a carbide ring in its base will size bulged crimps on the longer cases that you never trim and can hang up in your barrel.
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