When working up a load, you have to tune the ammo to the rifle. For example, you can load up 1 bullet and select one powder and try multiple powder charge weights like 41.0, 41.3, 41.6, 41.9, 42.2, etc. This will show you what the rifle will like and where the powder charge needs to be. See the target below. It's a 243 Win with a 115 DTAC shot at 300 yards. I like this target example, because it shows the perfect signs of reading the rifle and what the rifle likes. Center was Load A (the first and lowest powder charge) and showed an open group so I only shot 4 rounds. Load B low left, still open and not very tight. Load C top left is getting tighten, and stringing a little. (This stringing tells me I am approaching an accuracy node). Load D top right, shoots very tight about 1" at 300 yards. I was able to dial in this bullet with 1 powder tuning the charge to the rifle.

When you pick multiple powders and bullets, and pick 1 bullet and 1 powder and powder charge at random, there's no way to see what the rifle is telling you on the accuracy node or where you can dial in that combo (bullet and powder) next with those components. All your looking at is how that certain combo does, hoping you get lucky with a group. I'd recommend selecting 1 bullet and 1 powder, and working with that one combo one at a time on tuning the load.