Sure, you can use a regular backpack as a range bag. But with all of the purpose-built bags on the market, I don’t see why you would want to use a regular backpack. It’s just so much easier and more convenient to use something that was designed for range use than to try and retrofit something that wasn’t designed to carry guns, ammo, and other shooting gear. It’s kind of like using a bunch of milsurp .50-caliber ammo cano instead of one of the MTM 4-Can Ammo Crates. Work smarter, not harder.