You should not be having ignition problems with Pyrodex in a New Englander. If it's a "first shot" problem you're probably leaving a little oil or gunk around the nipple. Just for kicks, next time out, pull the nipple before your first shot and (1) make sure the base is clean and the flash hole is open, and (2)swab the channel under the nipple with a pipe cleaner. Bet it solves your problem.

My hunting load with my New Englander is 90 grains Pyrodex RS and a 385 grain Great Plains conical. DEADLY.