I walk a load up differently depending on if there is data for that powder or not. I have loaded hundreds of loads with mil-surp powder with ZERO load data out there for it, and I will start 10-15% below normal charges for similar burn rate powders, but walk up in a rather coarse 1-2% until I get near the wall.
I bought 32 pounds of surplus bulk IMR4895 all the same lot.
It did not act like canister IMR4895.
But after experimentation I realized it does have the same speed and density that H322 in the Quickload library has to within 1%.
The threshold of loose primer pockets is then predictable for the 243, 257RAI, 260, 270, 308, and 8x57 with the same case head strength ~ 72 kpsi before subtracting margin.
I got many pounds of Herters 164 with NO DATA.
I assumed worst case it was fast pistol powder.
I worked up a load in 35 Whelen, until I convinced myself it was comparable to Unique.