From The Bench: LMT MARS 308

Published on March 7, 2025
Duration: 36:16

This guide details the assembly of an LMT MARS-H .308 rifle, featuring a 13.5-inch barrel and monolithic upper receiver. It covers lower receiver preparation, trigger and ambidextrous controls installation, buffer system assembly with castle nut staking, barrel and muzzle device mounting with precise torque specifications, and the addition of optics and accessories. The build emphasizes LMT's unique barrel attachment system and compatibility considerations.

Quick Summary

The LMT MARS-H .308 rifle build utilizes a monolithic upper receiver and a unique barrel attachment system secured by two T30 Torx screws torqued to 140 inch-pounds. The lower receiver has a Knight's Armament style cut, making it incompatible with DPMS uppers. Proper assembly includes staking the castle nut for security.

Chapters

  1. 00:00Introduction to the LMT MARS-H Build
  2. 01:26Lower Receiver and Trigger Installation
  3. 04:07Grip and Buffer Assembly
  4. 09:29Upper Receiver and Barrel Installation
  5. 13:53Muzzle Device and Optics
  6. 16:48Final Accessories and Assembly

Frequently Asked Questions

What are the key features of the LMT MARS-H platform?

The LMT MARS-H is a monolithic large-frame platform known for its interchangeable barrel system. Unlike traditional AR-style rifles, it uses locking screws instead of a barrel nut for barrel retention, allowing for quicker barrel swaps and consistent torque application.

What is the correct torque specification for the LMT MARS-H barrel screws?

The LMT MARS-H barrel is secured by two T30 Torx screws. The recommended torque specification is 140 inch-pounds. Exceeding this or using foot-pounds can damage the rifle or tools.

How is the castle nut secured on the LMT MARS-H buffer assembly?

The castle nut is secured using a staking method. Metal is driven into the notch on the receiver extension using a punch and hammer, creating a non-permanent but secure lock that prevents the castle nut from loosening.

What are the compatibility considerations for the LMT MARS-H lower receiver?

The LMT MARS-H lower receiver features a Knight's Armament style cut in the rear. This means it is not compatible with standard DPMS-style AR-10 uppers; it requires a compatible LMT upper receiver.

Related News

All News →

More Gunsmithing & DIY Videos You Might Like

More from Brownells, Inc.

View all →