Speaking of large muzzle flash, back before the defense ammo craze really heated up, around 2003 or so IIRC, Frangible and RUAG came out with this 75gr 9mm that was ++P++ insanity, pushing close to 2000fps in a 4.5+in bbl. I shot a bunch out of my G26 - despite the factory warning me that they had nicknamed it "Glock Breaker" due to it killing 2 test pistols in less than 2000 rounds (that kind of pressure + tiny steel inserts in a polymer frame = catastrophic failure formula number one). Anyhow, the flash in the dark rivaled that of my 7" DPMS AR upper - I have some old video somewhere, it's a beach ball, a large one, and would absolutely be an issue if shooting in the dark, it's blinding. Loud too.