I've started loading 308 for a M1a and many recommended using a head space gauge. I bought a L.E. Wilson and cleaned some once fired brass, a mix of Federal, R-P and Hornady. I started adjusting the die down and ran out of adjustment with every case still just proud of the top of the Wilson gauge. I tried some unfired factory ammo and it drops in perfect. The dies are Lyman AA. Old (1970's) but looked unused when I got them in some trading. I would think 308 then is 308 now. What am I missing?