For the M sized motors I've used and what my mentors in the L3/research arena use ; a .50 cal BP pellet for muzzle loaders. Tape one to an e-match and tape that to a small dowel. I've used two pellets on a 75mm M, but I'm told that a single pellet will work fine for the 75mm with a 3/4" or 1" core. My mentors usually use two pellets with large 98mm or 152mm motors.
I've made my own igniters from nichrome wire and my own pyrogen mix and they were used on motors up to M without a problem, but the BP pellets work very well and are much easier to make and use.
My advice, don't over think it. Simple is usually better. YMMV
