All I can tell ya is extrapolating from my 5.56x45.  

7 grains of Red Dot makes a dandy load with a 50 grain jacketed, just about equal to a .22 magnum rimfire in the 5.56x45 case.   Reduce about 1 grain for the .222 case being smaller.  Use a pistol primer!

10 grains of Blue Dot also works the same. Reduce to 8.5 grains for the .222 case.

Accuracy from my Stevens 200 bolt gun is outstanding.

Sorry I don't have any experience with cast.  I have never been able to cast those little bitty bullets well enough to try it.

Phil

Bill
Thank you for your detailed reply.
I inherited 10# of PB and have been loading for my auto pistols with it. Lyman 45th. ed. recomends 5.5 gr. as their acuracy load. I have an RCBS 55gr. bullet that wont shoot in the 43 Winchester am hoping for better results with the Martini. Spent most of yesterday for 45 usable bullets Worked out a system for Gas Checking them so they would size concentric. Little bullets old hands and eyes big problem. Gun shoots jacketed into less than 1/2" at 100. Want to do same with the cast. The gun is good enough the rest is up to me. I do not use the 6x24 Tasco for anything serious. I have a 24 Redfield 6400 for that. 
Tom