Some remmy shottys have detents in the mag tube that act as a plug. When you want to carry more than 2 rounds in the mag you have to drill those detents out. If you did that and wanted to change it back to a legal field gun you would need to cut a piece of wooden dowel to block the mag tube so it will only hold two rounds. No biggie, that is how my 1100 is and my mossy 590.
Hope this helps you out.