SIG MPX | Barrel Swap & Piston System Disassembly

Published on August 29, 2020
Duration: 8:41

This guide details the step-by-step process for disassembling and reassembling the barrel and piston system of a Sig MPX, as demonstrated by an expert instructor. It covers identifying necessary tools, removing retaining screws, servicing the piston, and correctly reassembling the components for proper function. The instruction emphasizes attention to detail for a successful barrel swap.

Quick Summary

Disassembling the Sig MPX barrel involves proving it clear, removing the front pin, and unscrewing two Torx fasteners. Heat may be needed if Loctite is present. The piston system is removed by rotating a retaining crescent 180 degrees. Proper alignment during reassembly is crucial for function.

Chapters

  1. 00:00Sig MPX Barrel Swap Overview
  2. 00:27MPX Barrel Kit and Calibers
  3. 01:06MPX Barrel Removal Process
  4. 01:50Torx Screws and Barrel Removal
  5. 02:53Piston System Disassembly
  6. 03:48Piston System Components
  7. 04:34Piston System Reassembly
  8. 04:51Installing the 8-inch Barrel
  9. 05:12Related Videos and MPX Mechanics
  10. 05:45Barrel Reinstallation and Securing
  11. 06:35Final Assembly Steps
  12. 06:53Bonus Gun: M60 E4 Mod 1
  13. 07:44Closing Remarks and Future Content

Frequently Asked Questions

How do you remove the barrel from a Sig MPX?

To remove the Sig MPX barrel, first prove it clear, remove the optic and front pin. Then, unscrew the two Torx retaining screws, potentially using heat if Loctite is present. Once the screws are out, the barrel should slide forward.

What tools are needed for Sig MPX barrel and piston disassembly?

You will likely need Torx wrenches (sizes T25 and a smaller one) for the retaining screws and piston mechanism. A mallet might be necessary for stubborn parts, and a heat source could be required if factory Loctite is applied.

What is the function of the piston system in a Sig MPX?

The piston system in the Sig MPX uses gas pressure directed past ports to cycle the action. It pushes the piston forward, which then impinges on the carrier group, similar in principle to an AR-15's gas system.

How is the piston system retained in the Sig MPX?

The piston system is retained by a small crescent-shaped piece. This piece needs to be rotated 180 degrees, potentially with the aid of a small Torx screw or wrench, to allow for removal. Carbon buildup can make it snug.

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