The drawback here is what would happen with rolling for crits...not sure how this could hope to get around that (AC/10 does same crit damage but only rolls once, LBX10 essentially rolls 10 times, to my understanding).
If nothing else, your idea is great for solving the ammo issue - 1 single ammo type that gets consumed the same way at the same rate whether it's scattershot or solid shot, makes that easy and simple. (least that's how it appears to me)
I have a kinda trivial suggestion to tack onto this - to double the price of LBX ammo. Not that that truely matters, but still, balance y'know, since it would be doubling as two different ammunition types.
Edited by Telmasa, 20 March 2015 - 02:05 PM.