Well I went out to mom and dad's place yesterday at dusk with some 80gr blanks. Fired a cap to clear out the nipple and channle. Loaded the first blank, clean cut with a tiny amount of powder spilled on the breech block. Capped.....BOOM! Went off without a hitch. Had dad watching, he said there was a massive fireball out the muzzle but little to no flash from the area of the chamber on that, or the subsequent blanks.
I also noted not being peppered in the face with anything around my shooting glasses. I'm going to take this as a good sign as I'm assuming blanks would produce much less of a gas seal as a live round since there is little to no pressure.