Hi Jake.  I just bought and received 1k of your 69g BTHPs and am getting to start working up a load.  I built a clone MK12, with an 18” FN barrel.  I’m planning a MK262 clone, but will use your 69s instead of the sierra match 77s.   I found your post from 2021, in which you said 24.6g of TAC pushes these 69s to 3150fps out a 24” barrel.  You suggested you use the same load for 18” barrels.  
What charge did you start with, before settling on 24.6g of TAC?  I’m really interested in this ladder dev….