I use an RCBS mic gauge to measure spent rounds for headspace when I'm reloading 223.
I've just started reloading 300aac and there's no mic gauge for that.
So here's my idea... When I drop a spent round into the factory crimp die the shoulder comes to rest on the split collet.
The base of the round is slightly recessed into the die at that point. If I measure that distance I have a defacto measurement of the distance from shoulder to base on the cartridge.
If my resized brass match that distance minus a few thousands then I'm in the right ballpark with headspace aren't I?
I've never heard of anybody doing it this way, but I can't see why it would be less accurate than the mic gauge as long as I have a good measuring tool.
Am I missing something?
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