3-Round Limiter Compatibility Test | C.A.R.L for Super Safeties

Published on February 26, 2026
Duration: 7:45

This guide details how to fix a 3-round limiter (C.A.R.L.) that causes more than a three-round burst due to improper hammer and cam rotation. The issue often stems from the third sear's interface with the cam. Expert instruction covers adjusting or trimming the sear to ensure correct functionality.

Quick Summary

To fix a C.A.R.L. 3-round limiter firing more than three rounds, adjust the third sear. If it contacts the hammer, bend it outward. Alternatively, trim the sear where it meets the cam. This ensures proper hammer and cam rotation, essential for the limiter's function, especially in AR-15 platforms with milspec triggers and Super Safeties.

Chapters

  1. 00:02Intro: 3-Round Limiter Test
  2. 00:26Sponsors & Disclaimer
  3. 00:40Compatibility: AR-15 vs AR-9
  4. 01:08Milspec Triggers & Selectors
  5. 01:36Hammer & Cam Rotation Issues
  6. 01:55Fixing Cam Rotation: Sear Adjustment
  7. 02:21Role of Suppressor Back Pressure
  8. 02:45Testing on ST-50
  9. 03:40ST-50 Warning & Alternatives
  10. 04:01Discount Code Mention
  11. 04:1122LR AR-15 Test Setup
  12. 05:1322LR AR-15 Performance
  13. 06:059mm PCCs (AR9s) Challenges
  14. 07:01Conclusion & Future Products

Frequently Asked Questions

How does the C.A.R.L. 3-round limiter work, and what causes it to malfunction?

The C.A.R.L. limits an AR-15 to three-round bursts by controlling hammer and cam rotation. Malfunctions, leading to more than three rounds, occur when the hammer doesn't travel back far enough to fully rotate the cam, preventing the sear from engaging correctly. Suppressor back pressure can help ensure proper rotation.

What modifications can fix a C.A.R.L. 3-round limiter that fires more than three rounds?

To fix a C.A.R.L. that fires more than three rounds, you can adjust the third sear. If it touches the hammer, gently bend it outward. Alternatively, trim the part of the sear that interfaces with the cam to ensure proper engagement and rotation.

What firearms are compatible with the C.A.R.L. 3-round limiter?

The C.A.R.L. is generally compatible with AR-15 platforms using milspec triggers and Super Safety kits. It has been tested successfully on .300 Blackout, 22LR AR-15s, and some specific models like the ST-50. It often does not work with AR-9 PCCs due to differing internal geometries.

Are there specific trigger parts or selectors that affect C.A.R.L. compatibility?

Yes, the C.A.R.L. requires a trigger group that allows sufficient hammer back-travel for cam rotation. It works with standard Super Safeties (e.g., Hoffman Tactical, Arcfire) but may not function with selectors like the Atreus if they lack the Super Safety cut, or in AR-9s with non-standard parts or hydraulic buffers.

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