I was watching a product review of the R1 on youtube and the the reviewer mentioned that the buttstock was interchangable with (I think) the M2 shotgun stocks. So I'm wondering if 1: That is true and 2: Is that true with the MR1 as well. The reason being I'm a Californian for pity's sake!! We are dying for AR alternatives. We already own a mini-14 but frankly I find it somewhat lacking and outfitted with a ComfortTech stock I think the MR1 would be 100% CA conpliant so can it be done?