Don’t know for sure, but no less than 1k. For the recipe I use and the recoil it created, the Popple holes were ideal. So it depends what kind of recoil you have, and if you are able to add a few grains to compensate for the loss of power w the holes. Also, if you are shooting major, you gotta keep in mind how high your PF will become once you add more powder to the case. It’s a matter of preference. No one perfect answer. Good luck.