Putting an FRT in a .308 Sig Spear! And the MPX, Rattler & Virtus! All of them!

Published on June 13, 2025
Duration: 8:59

This guide details the installation of Frankenstein Armory trip bars, enabling Forced Reset Triggers (FRTs) on Sig Sauer MCX and MPX platforms. It covers identifying the correct trip bar variant ('Lite' or 'Heavy') for specific models and calibers, emphasizing the need for careful installation and a thorough function check to ensure safe and correct operation. The process requires adherence to safety protocols and potentially specialized tools.

Quick Summary

Frankenstein Armory trip bars enable Forced Reset Triggers (FRTs) on Sig Sauer MCX/MPX platforms. Available in 'Heavy' (Spear .308/.277 Fury) and 'Lite' (MPX/Rattler/Virtus/Spear LT) variants, these bars are made from heat-treated 17-4PH Stainless Steel. FRTs are legally distinct from machine guns, requiring one pull per shot, and testing shows good reliability in 5.56/.308 but some inconsistency in 9mm MPX.

Chapters

  1. 00:00Sig Spear .308 FRT Shooting
  2. 01:49Frankenstein Armory Trip Bars Introduction
  3. 02:40Platform Reliability Issues Discussion
  4. 03:09Legal and Technical Operation of FRTs
  5. 03:33Lite vs. Heavy Trip Bar Explanation
  6. 04:31Competitor Comparison (Midnight Machine)
  7. 05:16Caliber Reliability Results
  8. 06:09Shooting Demonstrations

Frequently Asked Questions

What are Frankenstein Armory trip bars designed for?

Frankenstein Armory trip bars are specifically engineered to enable the installation and use of Forced Reset Triggers (FRTs) on Sig Sauer MCX and MPX platforms, including models like the Spear, Rattler, and Virtus.

Are there different types of Frankenstein Armory trip bars?

Yes, Frankenstein Armory offers 'Heavy' trip bars for the Sig Spear .308 and .277 Fury calibers, and 'Lite' trip bars compatible with the MPX, Rattler, Virtus, and Spear LT models.

How do Forced Reset Triggers (FRTs) differ from machine guns?

FRTs are legally distinct from machine guns because they require a separate trigger pull for each round fired. They do not fire continuously with a single pull, and recent legal rulings have upheld this classification.

What are the reliability findings for FRTs on different Sig Sauer calibers?

Testing indicated strong reliability with 5.56 and .308 caliber Sig platforms equipped with FRTs. The 9mm MPX showed some inconsistency, which might be related to the generation of the magazine used.

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