Why REAL concials produce aflier ... who knows. It happens to me as well. It could be the lube, the way the conical was casted, the wad, the loading pressure uses, they way they engaged the rifling, just about anything. All you can do is try and be consistant and keep everything the same. That is one reason I do not trust them past 100 yards when hunting.

I have a friend and all he hunts with are the 300 gr REAL (that I cast)out of his .54 hawkins. He has never had a deer walk away after being shot. But his problem is, he (like me) does not trust them past 100 yards. I have shot hundreds, maybe even a thousand REAL conicals. I make them for both the .50 & .54 caliber in both weights. Just as you describe, I will have a very good group going, and all of a sudden for no reason, I get a flier.

Try and stay consistant and see if it solves itself. The Lyman you have looks like it does a good job with them.