Gunsmithing Installing a Sig Collapsible stock on a standard AR15 lower

the scallop cuts you'd need would go right through the thread iirc, and the adapter that goes on the back of the lower isn't set up for it either.

I've not seen any MCX standalone lowers for sale that weren't the price of an entire new MCX anyway, so I'd say get a new MCX/MPX pistol of your choosing and mix and match uppers and lowers to wind up with the two setups you want


personal opinion, after using the thin folder and the collapsing, the thin folder with the cheekrest and a little foam padding wins by a country mile (see pic)