I have been working on a new MGM 6mm x 223, which is nothing more that a 223 case necked up to 6mm, Contender pistol barrel for the last month or so. And have been able to find a fair amount of Jacketed bullet loading data but cast is non existent. The accuracy that I have gotten so far with various weights of jacketed bullets, both at 50 and 100 yds. has been quite surprising for a Contender pistol using Win. 748, Hodgdon BLC(2) and IMR 4895.
The only reduced cast load that I used so far has been with the NOE245-80-FN GC and IMR 4895 and using Hodgdon's 60 per cent rule. It has proven to be a good one.
However, I want to try these powders that have produced good results in cast loads for me in the past.
A 2400 - maybe, depending on how small of a charge in that small 223 case.
None of these are listed for jacketed in the loading data that I have.
So. the question is -- Being the overly cautious pilgrim that I am and because of lessons learned in the past, How can I come up with a safe starting charge for the above powders in that 6mm x 223 for 80-85 and 100+ grain cast bullets.