The KPS-3M Mongrel is Kang-Petrov's modular SMG platform designed to accept components scavenged from other weapons. The receiver has universal attachment points that mate with barrels, stocks, grips, and magazines from over forty different weapon systems. A Mongrel might have a Tessera barrel, a Crucible stock, and a Meridian magazine, all functioning together through Kang-Petrov's universal interface system.

The base Mongrel kit — receiver, bolt, and basic furniture — costs Φ300. Everything else is salvageable. Kang-Petrov publishes compatibility guides listing which components from which manufacturers fit the Mongrel's universal interface, and the community has expanded this list through experimentation. The weapon's reliability depends entirely on the quality of components used — a Mongrel built from premium salvage outperforms a Mongrel built from garbage.

The KPS-3M exists because weapons break, get abandoned, and accumulate in conflict zones faster than they can be manufactured or disposed of. The Mongrel transforms this surplus of parts into functional weapons, recycling the detritus of violence into tools for survival. It is simultaneously the most innovative and most desperate weapon in production.