Well, the 748 is ball powder, so that makes sense.
I did load some 748 up awhile back with large rifle primers and noticed some uneven velocities. I just now noticed the little asterisk that says magnum primers used, so I'll head to the store.
The Speer manual says they used CCI primers 200 and 250 in .30-.30, and the ones I have are marked 200, so the 250 must be the magnums. The Winchester primers I have are marked WLR, which I assume means Winchester Large Rifle. I may also pick up another powder, just for comparison and since the 748 requires magnum primers.
I bought 748 because there were loads listed for it in almost all bullet types, and I wanted to try some of the small plinking bullets at 100 grams as well as the 150 and 170. It seems like for IMR and Vita they have used one powder for the light bullet and others for the heavier bullets, which is not very convenient for low-volume reloaders like me.