This is a good question that I would like to know as well. Obviously the FCD can really put the squeeze on, but how much is too much or too little?
Here are two photo's, the first one is of a commercial "Alaskan Backpacker" 335gr 45LC which are suitable for Ruger or 1894's but not Colts. The crimp is way more aggressive than anything I am doing with my 45/70 FCD as the second photo shows. I want to figure a way to know how much crimp to use without going overkill and overworking the brass, or worse, too little. Hopefully some more people will post some pictures of their crimping to gage by.