It's not going to hurt anything, just might get leading to have to clean out.If they fit your bore well then no problems. 2400 may not throw as much flames as say H110.
The MBC formula is really just an estimate. I have asked Brad(owner) about it
Why would 230 gr 45 ACP bullets be the same 18 BHN as the 240 gr 44 Mag bullets???
If yours are 15 then that is in the middle of the MBC 12 to 18.
I would shoot them, I clean my guns after 5 or 500 rounds.
