The Alliant data is actually the highest that I saw in determining a ladder when I developed the load. Without going into detail, I had 25-30 different loads from numerous different sources. I considered the "least reliable" to be data from various reloading forums and the most reliable to be from various bullet manufacturers, both plated and FMJ.
Loads ranged from a low of 4.2gr to a high of 5.7gr (Alliant), with the overwhelming majority in the 4.5 to 5.2gr range. In the back of my mind I kept aware of the fact that the traditional government load was always 5.0gr. My test load ladder was 4.6, 4.8, 5.0 and 5.2. 4.6 was weak and less accurate than I'm used to, 5.2 was a little too stout and 4.8-5.0 (my Pro Auto Disk drops 4.9 consistently) seemed to be the sweet spot.
After all of this, when I actually looked at the bullets I was given, they're not FMJ as described, but instead they're plated just like I've been using. I'll stick with my 4.9gr load.
Thanks to everyone for your comments.