You have more issues to consider than just the magazine length. The 500 holds the barrel in place with a bolt that threads into the end of the magazine tube. The 590 uses a ring attached to the underside of the barrel, that slides over the magazine tube and is held in place, not by a bolt, but by the magazine cap. In both models, the magazine length is critical for the attachment of the barrel. If you want a shorter magazine tube, you will have to get a different barrel, which might be a gunsmith situation, rather than something you can just purchase and spin on.