About 45 years ago when I was young and inexperienced, I was given some 7.62mm LC brass from a brother-in-law who was a rifle range leader at Fort ? (I forget) while in the National Guard. Having only one rifle, a .243, I tried the same operation, with the same results. A little research later I was successful.
First step is to
size and deprime with a .308 sizer. Then remove the expander rod in a .243 sizer and size again with the .243 sizer.(you'll find it makes necking down much easier too. Then inside-ream the necks (did that on my Forster trimmer with a
special reamer they make just for that).
Everything else is the same process for any other .243 case. I loaded them with Speer 105 grain soft points over IMR 4350. Winchester primers were used after removing the crimp with a utility knife. Didn't have a swager or pocket reamer back then.
I never throw anything away....so all these years later, I happen to have three cases left necked down but never loaded; and one finished round I never shot, to remind me it can be done. Took a picture tonight for your entertainment!
View attachment 1104370
Yup....old 1968 Viet Nam era brass.
Now......did I make of habit of this? No sirs! Too dang much work. I saved the rest of that LC brass for when I bought a .308 rifle!
Brass as old as mine was hard even then. It won't swage worth a darn. Often it just shears a sliver of brass and leaves it in the pocket .... to make primers proud enough to slam fire in an AR 10. (did that three years ago...scared the hell out of me.) So get a primer pocket reamer and get rid of the crimp that way.
Thinking since I first posted, I had to correct one major detail...it was a lot of years ago. The nice helpful salesman at Forster, I called, told me over the phone to size first with .308! Which I did and it deprimed fine without getting stuck. THEN I resized it with the .243 sizer without an expander rod, Final stip was to I.S. ream the neck to thin them. Fixed the original content in red.