Both the Remington 870 and Mossberg 500 probably have the most aftermarket tactical modifications / accessories available . The new Remington 870 Fieldmaster pump by new owners RemArms appears to have upped the quality , smoothness and reliability of the former Remington 870 Express . Not much to say new regarding the Mossberg 500 pump as it remains a solid , reliable choice as ever . Which would you choose as a HD project gun for HD and why ?