I shoot a lot of .223 and many years ago decided handloading was the way to save money. I collected cases from all my friends who didn't reload and also picked up all the discarded brass at the range. I was reading Machine Gun News and heard about a MG shoot at Hot Springs AR. Once I decided to attend I figured on taking my M-16 and 25-30 loaded mags and as much as I could on strippers... a lot of reloading to do!
Knowing I would be loading a mixed bag of brass, I unlimbered my Dillon electric trimmer setting the approx length by screwing in the trimmer die until it just touced a properly trimmed case mouth. The first round or theree came out as still too long so I screwed the die in further until I got to the right length and proceeded to trim 1,000 rounds.
At the shoot I started getting full head separations. The bolt just wouldn't close all the way and I couldn't see the case half stuck in the chamber. Mr. J.A. Ciener finally came to my rescue and helped clear the problem, advising me not to shoot any more handloads in my full autos.
The problem was the trimmer die. I thought it was merely a hollw connection from the trim motor to the press. Ain't so. It is actually a size die and if you screw it in too far you move the shoulder back causing excess headspace. Moral of this story is "get a cartridge headspace guage and use it!" :-D
