Start with 45 grains fff and go up in 5 grain increments until you get the best group. Max load would depend on the barrel make, but I would think about 90 grains. My guess is you will end up somewhere in the 65-70 grain range. Getting harder to find factory .45 cal lead conicals these days, but you could buy them from some guys on this forum and decide which ones work best for your gun.