By the time you have all the moeny and time into it you would probably be better off just buying a new stock unless your idea is somethign that isn't redily available. I have tried to modify factory stocks and I never have good luck with it. I can build a wood stock from the ground up with less hassle than trying to extensively modify a factory plastic stock.
There are people out there that can do it with great results, I am not one of them.
Just my thoughts
Dolomite
Bookmarks