Well, my guess is that you have Laflin & Rand powder there, my friend!  I've taken apart a few of my old FA rounds (with cracked necks, easily pulled apart with fingers) and the powder looks identical.  I would bet that even the ones without cracked necks were not actually fit to shoot (although about 10 years ago, I did use the powder and bullet from one once to load into a new brass, and it fired just fine).  My guess about the powder weights is that it's from degradation... as they should have started out at 40 grains.

I have several pieces of the UMC .30 USA and U.S.C Co .30 GOV brass.  I haven't used them with my match ammo... but I did use some with my cast bullet loads.  Of course, they were all fine with no cracks.