So I just picked up some Suprema 00 buckshot from Walmart for really cheap. I went out and shot 3 rounds and then inspected the inside of my barrel. There is a huge buildup of lead rubbed along the sides that took 10 runs thru it of a bore snake to clean out. But the other problem is that there are some pretty heavy scratches in the inside of the barrel now. So I guess my question is would it be bad to keep shooting this ammo if it does this to my gun? Another thing to note is that looking at the shells up to a light source there is no wad that goes up the sides just a small plastic cup to separate the shot from the powder. I have an 870 tactical with an 18.5 inch barrel cylinder bore choke. Thanks

Those are not scratches. Lead will not scratch steel. More than likely lead buildup on the barrel steel, Run a bore brush with Hoppes #9 thru there a few times. Bore snakes don't remove anything but powder residue.
Beware "Really Cheap".

It should not be leaving scratches, if it is then there is something really wrong with the ammo. Nothing in there should be harder than the barrel.

Most likely it is, as has been mentioned, lead buildup and fouling. If the buck is not held in a shot-cup it will be rubbing the length of the barrel and will leave a buildup over time. It should come off with a little solvent.

Let us know how it works out.

Try a product like Gun Scrubber and some elbow grease using a bore mop...

So do you guys think shooting this ammo will be bad for my gun? I bought 100 rounds since it was cheap and really don't want to waste it. Although once this stuff is gone I'll just fork over a few more bucks to get some quality stuff

Well guys I got her cleaned. I ran a bronze brush thru it a few times to loosen the lead up then a mop with some hoppes number 9 on it and she came completely clean. Thanks for the help

Good to hear!!

I think you will be just fine shooting the remainder of your ammo. I've bought a LOT of cheap ammo over the years just for range time.