If it's an actual 1861 Colt Navy, it would be .36 cal., in which case loading a .451 ball would be quite a task. The .44 cal model Colt would be the 1860 Army.
I'll wager you really do have something the (really dumb) manufacturer labeled as they did, but historically, the models I've mentioned were as Colt made them.
If you have a .44 cal. model CVA whatzis, you will find that around 23 gr. 3F will give you optimum accuracy.
If it really is the Navy model .36 cal, then 17 gr 3F will be the most accurate load for a .375" roundball.
Well, I'll just hop into my Chevy F150, or Honda Prius, and mosey along now...