I've had good luck with IMR 4895 in 308 with good accuracy, but dropping all the way down to 60% seems too low. Within reason 4895 seems ok.
I use cast data, and estimate charge weight to keep pressure above 40k on the low end. That seems more reasonable to me to get a complete burn and recoil is very soft at that level. Closer to 80%. 60% may be safe but I think it's better to use a faster powder as suggested.
For consistency, you want enough powder in the case so the primer can find it.
I know guys that use a case full of 4831 behind cast bullets to keep velocity low enough to prevent leading. Pressure and recoil is low and ignition is not an issue.
