The rifled shotgun barrel is for use with sabot slugs ONLY.
NO birdshot, buckshot, or standard slugs.
Use with lead shot or buckshot will:
1. Lead the bore up BADLY, and is very hard to get out.
2. It shoots donut-shaped "patterns" with a big hole in the middle. Hits on target are a matter of blind luck.
Doesn't actually damage or ruin the steel barrel since lead is much softer.