Simple to mod out the SPS-12 but I had a hell of a time finding Chinese tooling die/taps. The quad rail is from a g3, the charging handle was knocked out on the Bridgeport as well as the piccatinny (the speed bead is not installed yet) the knox was from an 870 - a little machining required, but its probable that it will need to be pinned in one position - I got about 300 in it (gun was bought at 100) without the sight and light. The retail on these has shot up significantly and they are now running at about 400-600, the big loss for this platform is mag's are unattainable, would have loved to