I have not had good luck yet with my 03 shooting cast. I have tried .308 and .309 bullets to no avail.
Tried lots of powders/charges and different lubes, all GC bullets.
My bore slugs .3085 - .309 and looks new, CMP gauge is less then 1 muzzle wear.
Should I try 170gr. Lyman 311291 sized .310 - .311
Also would it hurt to try a 185 grain .311 RN for the .303 Brit. in my 03 ?