Lead bullets certainly have an easy trip down the bore compared to jacketed, and I can 'see' ignition problems with slower, more difficult to ignite powders.

Some guys have gone to using 'starter' powders to get the burn going. Even in yesteryear, these types of loads were developed. A bit of 3f will help - reduce the main charge about 1gr.smokeless per 3 of BP. It should only take acouple gr.s of black to get the smokeless cooking. Start about 3 or 4gr. grains down from current loads and work back. Just a suggestion. By all means, use a Fed 215 if you want, but a normal mag primer should suffice, like a WW or a CCI. RP 9 1/2 mags are slightly smaller in size if you have tight pockets.