The reason for hornadys recommendation is because the FTXs are supposed to be used in short cut cases. the OAL isnt gonna matter in your BH because the cylinder will accomodate 1.7" cartridges. Max OAL for the .45 colt is same as .44 mag at 1.6. so you have a 10th of an inch to play with. Use a starting charge for 225 grain bullet and seat them to the cannelure and measure them. if they are at or below 1.7" just crimp them and develop a load like normal with regular 225 gr data.