Re: 5.56 with Dillon 550 what dies?
Ky Patriot,
A case gage is a tool that helps establish or measure case dimensions, such as headspace. They're an absolute necessity to correctly set up dies and ensure that you're not bumping shoulders back too far, while still making sure that the rounds will chamber properly. Wilson and Dillon both offer drop-in chamber type gages. That is, drop the loaded round or case into the die, and there's a series of measurments that can be taken from that point; headspace, case length, etc.. Very easy, and will save a lot of trouble down the road. The RCBS Precision Mic is a two-piece gage that has a vernier scale on the top piece, allowing you to get an actual measurment on each case, and see just what's going on when you're setting dies up. Bump gages, such as those offered by Hornady and Sinclair will also do this, allowing the handloader to get a measurment off the datum line, and adjust accordingly. All good tools, and I can't recommend them highly enough. Frankly, I wish more reloaders would use them. They'd avoid a lot of headaches.