Does a Weapon Mounted Light Affect Point of Impact?

Published on October 14, 2021
Duration: 11:26

This video investigates whether a weapon-mounted light affects a firearm's point of impact. While the presenter initially suspects it does not, the testing suggests a potential, albeit minor, shift. The primary takeaway is the critical importance of confirming zero after any modification, especially when accessories might exert pressure on the barrel or gas block.

Quick Summary

Weapon-mounted lights generally do not affect a firearm's point of impact unless the mounting hardware causes screws to press on the barrel or gas block. Factors like muzzle devices, suppressors, and barrel pressure are known to shift POI. Always confirm your zero after any accessory changes to ensure accuracy.

Chapters

  1. 00:00Introduction: Assumptions and Unknowns
  2. 00:27The Comment: Light Affecting Point of Impact
  3. 00:48Defining Point of Aim/Impact Shift
  4. 01:16Initial Skepticism and Testing the Theory
  5. 01:44Stripping Flashlights for Initial Zero Confirmation
  6. 02:02Testing Methodology: Tripod, Red Dot, Magnifier
  7. 02:37Factors That DO Affect Point of Impact
  8. 02:40Muzzle Devices and Point of Impact
  9. 02:55Suppressors and Barrel Harmonics
  10. 03:06Pressure on the Barrel (Barricade Shooting)
  11. 03:17Free Float vs. Non-Free Float Rails
  12. 03:51Mounting Flashlights Back for Testing
  13. 04:10Live Testing the Theory
  14. 04:58Walking Down Range to Analyze Results
  15. 05:03Potential Cause: Protruding Screws on Gas Block
  16. 05:34Checking Screws for Barrel Pressure
  17. 06:00Ammunition Used: Low Quality Range Ammo
  18. 06:13Comparing Groups: Without vs. With Flashlight
  19. 06:37Alternative Theory: Gas Interference
  20. 06:57Analyzing Group Centroids
  21. 07:30Conclusion: User Error vs. Equipment Shift
  22. 07:37The Golden Rule: Confirm Your Zero
  23. 07:59Specific Warning for M-LOK Rails
  24. 08:15Non-Conclusive Results and Further Testing
  25. 08:24Reinforcing User Error Suspicion
  26. 08:30Reminder: Check Your Gear and Zero Often
  27. 09:13Visual Comparison of Groups
  28. 09:34Final Personal Opinion: Light Doesn't Affect Barrel Operation
  29. 09:44Double-Checking with More Rounds
  30. 10:00Identical Group Results
  31. 10:08Final Conclusion: Light Position vs. POI
  32. 10:17The ONLY Way a Light Mount Affects POI
  33. 10:34Why Mount Light at the End of the Barrel?
  34. 10:42Avoiding Muzzle Shadow at Night
  35. 10:52Running Suppressed and Light Placement

Frequently Asked Questions

Can a weapon-mounted light affect your AR-15's point of impact?

Generally, a weapon-mounted light itself does not significantly affect point of impact. However, if the mounting hardware causes screws to protrude and press against the barrel or gas block, it can cause a shift. It's crucial to confirm your zero after any accessory installation.

What factors are known to affect a firearm's point of impact?

Known factors include changing muzzle devices, adding or removing suppressors, applying pressure to the barrel (e.g., shooting from a barricade), and using non-free-float handguards that contact the barrel. Always re-zero after such modifications.

How can I ensure my AR-15's zero isn't affected by accessories?

The most reliable method is to confirm your zero at the range after installing or removing any accessory, especially lights, lasers, or optics. Pay close attention to mounting hardware to ensure no components are pressing on the barrel.

Why would someone mount a flashlight at the end of an AR-15 barrel?

Mounting a light at the end of the barrel helps prevent the muzzle from casting a shadow on the target area when shooting at night. This is particularly useful when running suppressed, as it can position the light past the suppressor's length.

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