British firm AEI Systems Ltd make everything from 30mm aircraft cannons to bolt action 7.62mm rifles. At DSEi 13 they had a new prototype .50 caliber anti-material rifle on display. The gun has a long action recoil system and curiously it is fed by two side-mounted magazines. The magazines are selectable, so you could load AP rounds in one magazine and HE rounds in the other.
I am not sure what scenario this gun was designed for. It is possible, I suppose, the idea is that it allows snipers to quickly switch to non-chemical/explosive rounds when targeting humans and switch back when targeting vehicles. This would avoid running afoul of the treaties and international agreements that in theory ban explosive ammunition against human targets.
I like the very deep fluting on that barrel and suppressor. That should help keep it cool when shooting in hot climates.