Unfortunately, the only real way to tell is to try them. Every gun patterns differently, even with the same load/choke combo. If your full choke patterns well out to 40 yards, go ahead and use it. Patterning isn't cheap or easy, you should try different loads in different sizes from different manufacturers and see what shoots best. Then try different chokes and do it again. Keep it up until you find a choke/load you're happy with.