950 Tourer,
It sounds like you may have something accurate enough that 50 yards, other than initial zero roughing, isn't going to give you a lot of information.
The half grain increments are fine for checking for pressure signs, but at about 2% of load are about twice what I would use looking for minimum group sweet spots. Ideally, you want to find a load that is maximally accurate and works across a charge weight span of at least 0.5 grains so you don't have to fret small errors from the powder measure. Take a read through
Dan Newberry's OCW system. Like all the load ladders, it will work most clearly at about 300 yards in zero wind conditions, but because the OCW runs three loads per charge weight it gives you resolution that can usually be figured out at 100 yards or at least get you very close there. An
Auddette Ladder, with one shot per load level is really hard to see clear results from at under 300 yards, though Creighton Auddette himself used it at 200 with benchrest guns, IIRC, and Randolf Constantine was the one who suggested 300 was a lot better.
Both of the powders you are using are canister grade (tighter burn rate tolerance than bulk grade) versions of powders in the St. Mark's Western Cannon (WC) series. 748 is canister grade WC748 and H335 is canister grade WC844. In 1989, CCI reformulated their magnum primers for use with these powders. That includes both the CCI 450 and #41 primers for small rifle primer pockets, the latter being geared to AR's, specifically, as it has the military sensitivity spec. The powders in this series have a heavy deterrent coatings that are harder to light consistently with standard primers, though I have found I could do it if I first deburred flash holes and got the powder over the flash hole at firing. Absent that, they did not ignite as consistently with a standard primer as with the magnum primers.
If you have a chronograph, you can test to see which primers produces the most consistent ignition for you by seeing which one produces the lowest velocity SD. Critical to that is setting the bridge of the primers properly, which means pushing them in a couple thousandths past the point where the anvil feet touch the bottom of the primer pocket. In other words, seating them on the hard side.