A SIG-Sauer MPX Gen 2 with a stock inspired by the SIG PSB collapsible brace appears as the “BAS-P”. It is Alejandro Vargas’ main weapon throughout the campaign, and was added to multiplayer on Season 1. It is part of the “Bruen Ops” platform, suggesting that the in-game manufacturer Bruen (which also manufactures the Bruen Bullpup/AUG platform) is a mishmash of SIG and Steyr.
The optional barrels are the following: “12″ Bruen SZ-36” (a fictional-length barrel with a Midwest Industries-style M-LOK handguard), “10.5″ Bruen Typhon” (an integrally suppressed barrel with an MPX Gen 1 style handguard), “6.5″ Bruen Drake” (with a factory MPX-style M-LOK handguard), and “4″ Thunderfire” (an MPX K’s 4.5″ barrel).
Equipping the “10.5″ Bruen Typhon” barrel turns the weapon into an MPX-SD.
Using the “4″ Thunderfire” barrel and the “BR Stockless Mod” turns the gun into an MPX K.