Most of the shot shells for pistols have the lead shot contained in a plastic container which also has a plastic (type) of gas check. The shot is pushed through the barrel of the gun, and the lead never touches the barrel.
I have been loading my own with a plastic case for years, I buy the cases from Speer, or from Midway. I usually load 50 at a time, and when they are close to gone, I load 50 more. They last for quite a while.
To keep things simple, I cut the end off a couple of 12 gauge #9, and use the shot from that to load with. If you know a skeet shooter, they may give you enough to load 50 rounds or so.
It won't hurt your gun.