Putting an FRT in all my LMT Rifles!

Published on January 14, 2026
Duration: 10:15

This guide details the necessary modifications for installing a Forced Reset Trigger (FRT) into AR-10 platforms with high-shelf lower receivers, such as LMT MARS-L and KAC SR-25 models. The video highlights that these specific lowers require internal milling to allow the FRT lever full clearance, preventing binding issues with the bolt carrier group. It also touches upon the inherent tuning challenges with FRTs on .308 platforms compared to 5.56.

Quick Summary

Installing an FRT trigger in high-shelf AR-10 lowers like LMT MARS-L or KAC SR-25 requires milling the internal shelf for clearance. AR-10 platforms are more challenging to tune with FRTs than AR-15s due to sensitivity to gas pressure and buffer weights, often leading to malfunctions if not properly addressed.

Chapters

  1. 00:00Intro & .308 FRT Shooting
  2. 01:24AR-10 FRT Tuning Challenges
  3. 02:11Technical Failures Explained
  4. 03:41Milling High-Shelf Lowers for FRT
  5. 06:09LMT 5.56 FRT Performance
  6. 07:59Spuhr BAM Mount Overview
  7. 08:34Final .308 FRT Testing & Conclusion

Frequently Asked Questions

What modifications are needed to install a Forced Reset Trigger (FRT) in an LMT MARS-L or KAC SR-25 lower receiver?

High-shelf AR-10 lower receivers like the LMT MARS-L and KAC SR-25 typically require the internal shelf to be milled or 'clearanced'. This modification provides the necessary space for the FRT lever's full range of motion, preventing it from binding or being obstructed by the bolt carrier group.

Why are AR-10 platforms more difficult to tune with FRTs than AR-15 platforms?

AR-10 platforms (.308 Win) are generally more sensitive to gas system tuning, buffer weights, and suppressor configurations when using FRTs. Issues like tolerance stacking and the FRT lever's interaction with the larger bolt carrier group can lead to malfunctions, making reliable function more challenging to achieve compared to 5.56 AR-15s.

What specific issues can occur when installing an FRT on an incompatible AR-10 lower?

When an FRT is installed on an AR-10 lower without sufficient clearance (like a high-shelf design), the bolt carrier group may catch on the FRT lever during cycling. The lever itself can also bind in its rearward position, preventing the firearm from functioning correctly and potentially causing stoppages.

Are FRTs designed for AR-15s compatible with AR-10 platforms?

Not necessarily. Components like the Arcfire FRT were not originally designed for the AR-10 platform. While modifications can make them work, users must account for the larger dimensions of the AR-10 bolt carrier group and potential differences in receiver geometry, especially with high-shelf lowers.

Related News

All News →

More Gunsmithing & DIY Videos You Might Like

More from Juicey Media

View all →