Only chain fire I ever experienced was with triple-trouble. Blew the front sight and the loading lever latch off my 1860. On the second shot of the second cylinder. Or, shot number eight. A fluke? Don't know. Shot that gun with black only for 20 years, never a chain fire, even without wads or lube. Has probably been ten years since, and never a chain fire. ? I suspect that even though it's harder to ignite, it may burn quite a bit hotter. I didn't know it had sugar in it.
Not too long ago, someone posted about 777 blowing the hammer back on their side lock, and damaging their lock. I've had dozens of hammer blow backs with rifles, if not 100. None ever damaged a lock. ? Fluke? Who knows. I'd use Pyrodex, if I HAD to, before I'd touch 777.