Both revolvers and semi-automatic pistols have barrels with lands and grooves, so I'm not sure what type of firearm it was. If you make your own ammunition, you can buy bullets in bulk in many types and profiles. I can't really see the pellets, so I'm not sure what kind of cartridge it was.
I often shoot at indoor pistol ranges, and there are people who aren't proficient hitting the concrete floor. After it hits such a hard surface, it isn't easy to tell what it was. If there are copper alloy remains, along with lead, one can assume it was a bullet with a copper jacket.