one of the problems in utilizing the inherent utility of the ar-15 gun platform is that people have always considered the use of cartridges larger than the 5.56x45mm nato if not impossible, then so difficult as to preclude an easy utility.
it's the matter of shoehorning a cartridge into an ar-15 magazine, so as to have the magazine fit into the ar-15 magazine well.
i am in the process of finishing a project in which "jj's brit" ™ will be fitted into an ar-15 rifle, with no modifications to the upper and lower receiver, save for the use of a barrel extension promoted by harrison beane at www.ar15performance.com , which i have written about earlier. there's been a bit of a problem, which harrison is addressing, but i am enthusiastic about the prospects of getting the whole thing to work.
as an expedient, we will be using pri's most excellent magazine for the 6.8mm remington spc, in order to house and feed the little "brit" in the completed rifle. it is not any slander on the pri magazine to note that this is less than ideal, as the pri magazine was designed to house a cartridge with a case head of around .410 to .416's, and was never intended to reliably feed cartridges with a .473" case head, such as my little brit.
but, i've figured a way that with an absolute minimum of violence to the ar-15 platform and its inherent limitations due to size, that a magazine housing a .473 case head cartridge can be used in an ar-15 lower, while still allowing the use of magazines designed for the 5.56mm nato. not at the same time, mind you, and not with the same upper, ... , we are talking about different cartridges and chamberings, what?
i've outline the process in the letter attached below.
for what it's worth, and given the sometimes futility of doing so in things involving firearm's manufacture, i assert intellectual property and trademark in the process described below. it is not a lengthy process, just a matter of some relatively simply machining, but no one else has described it or done it, to the best of my knowledge.
i call the process and end product of same, as "jj's dual purpose magazine well,"™ for lack of any better term coming from my meager imagination.
the process. (from a letter to a friend.)