Here is one of those little things that can make life as a gunsmith tough. A SAAMI drawing from 11/12/1938 shows a shoulder angle of 20 degrees and 48 minutes. There is a later revision in 1947 that retains that 20 degree angle. Jump forward in time to4/21/1980 and SAAMI issued a drawing with a 19 degree shoulder. Its less than two degrees so what is the big deal? Well the problem is the differnce in angle will cause confusion if not understood. The 19 degree gage, if used in an old style chamber will contact at the junction of the neck and shoulder, thus causing the headpace to appear tight, or tighter than it really is. You can chamber cast to see which chamber you have if need be. Is this a big deal? Not really, just one of those things that forces the gunsmith to check more details. You might have to check your gages because most are not marked as to shoulder angle.