well I found
This about the LAV-AD.
As far as the AA-12 shotgun goes I was going for an alternative universe build that is intended for combat in urbanized areas or in the sorts of wooded areas where the undergrowth gets really thick. From what I have read about the design it uses that long tube on the back of the reciver to hold a lengthened recoil spring. In essence it's a buffer tube. Technically it would be possible to mount a collapsing stock around said buffer tube. What I am looking at would be similar to what is described in one of the old Able Team novels. an AA-12 modifed to look closer to the visual profile of an M-16 varient and not an assault shotgun.