Vltor VIS preview
PREVIEW – Vltor Weapons Systems debuted their VIS (Versatile Interface Structure) upper receiver/rail system at the 2006 SHOT Show. It’s a one-piece (monolithic) upper receiver/rail system, initially manufactured in two separate pieces, then joined together by the salt dip brazing process.
Brazing is the process of joining two pieces of metal with a solder or filler metal with a high melting point, just below the melting temperature of the base metal. Simplisticly, the salt dip process involves immersing the pre-heated pieces in a molten salt/brazing flux bath, which heats up the part quickly and uniformly. The melted filler metal flows between the joints through capillary action, and when removed and cooled, results in an extremely strong and high-quality joint. One of the advantages of salt-dip brazing is that it enables designs which might not be possible through a conventional machining process. It is this process that enables the VIS to have a outside-threaded receiver-barrel interface that will take a standard barrel.
Note that the following applies to the pre-production prototype pictured here – the production VIS will have minor changes, and I’ll update this when it’s available.
The VIS is designed as a monolithic upper which takes any standard M4/AR-15 barrel. The only thing that needs to be changed is the barrel nut, which requires removal of the front sight base (a normally simple matter). The VIS comes with a proprietary barrel nut wrench. It’s not meant to be a quick-change barrel system like the MRP, but it’s possible to switch barrel assemblies relatively easily, if both have the barrel nuts already installed. No removal of the standard gas tube is needed.