Thank you all for contributing.
I'm thinking wheel weight lead, its what we use already and have a bunch of it. I want to stay in the 50-60gr weight range so I can stretch out to that 150yd distance and stay in squirrel head accuracy.
I have had multiple Martini's, Stevens Favorites and 44 1/2's etc. They wouldn't be a bad option, especially a Martini..
I could also go with a Hornet or something like that as suggested to save work and stay with a small case.
I would rather figure out what works best then build the rifle but my 222's are both 1/14" twist I believe. 788 and 722.
I'm wondering about a hollow point in the 50 gr range to allow for a longer bullet?

Is there a system to the Lyman mold model numbers?

Thanks again