Or Canadian buddies over at Cadex have been making cool specialized weapon accessories for a while and this 870 Butt-end is a great example. Made to go on the popular Remington 870, it not only allows the user to use AR style stocks, but allows a quick stock release as well. Breachers are certainly the main customer in mind, however having such an easy stock release is handy for other simple tasks such as more options for storage. The main magic is the piece between the receiver and the stock with the grip and stock needing to be supplied by the customer. Offhand on this setup I show a Hogue grip and AA TI-7 stock.

Once the old stock is removed, some being easier than others, installation of the Cadex Butt is pretty easy mostly consisting of tightening one big screw. An ambi sling plate came with this A-version which can be rotated to be setup for left or right side presentation. The only down side is the butt needs to be removed to flip the sling plate around. Alternatively the B-version comes with a plate with no sling connect slot if you planned on using only the QR connection holes (that comes standard on either version). I snuck in the Cadex handstop rail mount in the parts pics, which may be confusing, but I hope to show off properly later. The optional cover is shown which make a nice snag free and clean looking end result when the stock is released. To release the stock or cover the button is simply pressed on the right side to allow rock-out removal. The button protrudes very little while still being a good size to be able to engage with gloves for a solid balance of ease and security. As a nice bonus, the button does not need to be pressed when inserting the stock or cover, it will just slide on in and lock.

Made mostly of quality metal, the Cadex 870 Tactical Shotgun Butt can take plenty of abuse and as a result feels rugged as well. There is a little pit of play in the main connection joint, not enough to make me really care, I just wanted to make sure and note for those who may be more picky. Overall I think the design is well thought out offering easy use and not forgetting about modern sling options. If you don't already have a dedicated combat and breaching shotgun, the Cadex 870 Butt adds a lot of adaptability to a single shotgun.
http://cadexdefence.com/870p_tactical_shutgun_butt.html