I got invited to a night shoot several years ago (our range normally closes at sundown - this was a special event to which a few of the regular IDPA shooters were invited.) At the time I was competing with a Glock, and I was reloading 9mm using Power Pistol. Never noticed any fireball during the daytime, but those rounds sure lit things up in the dark. We were using flashlights to see the targets, so I didn't really get shut down with flash blindness. But the flash was very obvious, even with a flashlight, and the rest of the participants sure did gig me about the extra illumination I brought.
Later research showed that big flash was a known characteristic of Power Pistol powder. I still have a lot of that ammo, as I switched to revolvers and other powders for my 38 Special loads. (Haven't been invited to another night shoot, so don't know if Trail Boss has a big flash or not.) But if I ever need to replenish my supply of 9mm, I'll look for a different powder that has lower flash characteristics.