Be86 cast 10mm load

[longshot7.62x51]

Current load is 7.3 gr of be86 for a 180gr hap bullet. Load is snappy but accurate. Wanted to know how much to reduce the load for a 180gr cast lead. Pistol is a glock 20 with a storm lake 6.2 In barrel.

I have quick load but is dose not have be86 as a powder. Should I just reduce load by 5% and check for leading