When Vltor Weapons Systems debuted their VIS (Versatile Interface Structure) upper receiver/rail system at the 2006 SHOT Show, people also asked “since the VIS is made of a billet receiver joined with a rail, are you going to offer the new receiver by itself?”. That made a lot of sense to Vltor to offer the receiver by itself, and here it is: the MUR (Modular Upper Receiver).
The MUR the receiver-only portion of the VIS. The only difference is in the material used. The MUR is machined from a billet of 7075-T6 aluminum whereas the VIS is 6061, as 7075 cannot be salt-brazed. It’s hard coat anodized and dry film lubed on the inside.
The MUR is available in two versions – the 1A (bolt Assist model) and the 1S (Shell deflector model). A cutout in the right side of the receiver accepts either a shell deflector insert, or forward-assist/deflector insert, which give the MUR its ‘Modular’ name. However, the inserts are not meant to be switched out by the user, as improper assembly can cause damage to the receiver.