I agree with the others. Butter is best left for toast and bagels.

I use Butter as a round ball patch lube and for Wads when I shoot lead conicals, but otherwise it isn't needed for any type of Sabot or powerbelt.

For working up loads, when you're working with a total unknown setup, it's best to start at 25yds like cayugad mentioned. Personally, I'm confident enough in what my rifle does to start at 50yds............but that's as much experience as it is ego.

When developing loads or just practicing at the range, I always run both sides of a spit patch between each shot and maybe 2 such patches after every ten shots. The key to consistency is consistency (thank you Yogi Berra ). In other words, do the exact same thing everytime. Measure your powder the same way, load your bullet the same way, swab between each shot the same way.................... that way the only excuse for large groups is operator error or the load itself - and operator error can be greatly decreased by good bench practices.