I assume you mean being fired with live ammo, not dry-fired (empty, no ammo).
The less-expensive ammunition often used for target/range shooting has gunpowder that is not treated with flash-deterrent additives, so it tends to give off more sparks and muzzle-flash when fired. I recently took a friend to the range, and while taking some video clips of him shooting, I noticed some sparks flying out of the barrel; looked like a chunk of gunpowder still burning, like a tiny comet. I managed to find something similar on one of the still photos I extracted from the video clips (look for the 3-4 little lines coming out of the front of the flash):
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)