I know nothing of Firearms. (I own four)
I know nothing of Physics. (I Majored, with a Minor in Philosophy)
I know nothing of Practicality. (Does Anyone?)
I know nothing of Gunsmiths. (I am by No Means one)
I have Obsessive Compulsive Disorder. (it has to do with numbers, i want the power of two 7.62x51mm rounds in one round, that is... similar fps/trajectory w/ double the projectiles weight)
I have no need for Functionality. (This is about OCD not a Practical Firearm)
I have vast amounts of Disposable Income. (I Don't. this is a hypothetical question...)

now that we have all that cleared up... i want a C-Mag that will hold 100 rounds of 8.6x70mm (.338LM).

would it be possible for me to have someone make me this custom magazine? who would it be, a gunsmith?
oh and... i play too much call of duty, gears of war, and halo... and i watch too many zombie movies and cartoons on television.