The SIG-Sauer Spear AR (kinda)

Published on May 10, 2023
Duration: 10:10

This expert guide details the ambidextrous controls and upper receiver enhancements of the SIG Sauer M400 X-Series SDI, drawing comparisons to the Spear LT. The review highlights the fully ambidextrous lower receiver, including the right-side bolt catch, and upper receiver improvements like a repositioned forward assist and steel-reinforced charging handle latches. The assessment comes from a highly authoritative source with extensive experience in AR-15 platforms and competitive shooting.

Quick Summary

The SIG Sauer M400 X-Series SDI AR-15 features a highly regarded ambidextrous lower receiver, including a right-side bolt catch, and upper receiver enhancements like a repositioned forward assist and steel-reinforced charging handle latches. It has a 16-inch 4150 steel barrel and proved reliable over 1000 rounds, though its included optic, the SIG Tango MSR 1-10x, is criticized for image quality.

Chapters

  1. 00:00Introduction to M400 X-Series SDI
  2. 00:48Ambidextrous Lower Receiver Features
  3. 01:37Trigger and Upper Receiver Enhancements
  4. 02:53Barrel, Gas System, and Handguard Specs
  5. 04:24Muzzle Device Critique
  6. 05:38Accuracy and Reliability Testing
  7. 06:27Optics Review: SIG Tango MSR 1-10x
  8. 08:20Conclusion and Value Assessment

Frequently Asked Questions

What are the key ambidextrous features of the SIG Sauer M400 X-Series SDI?

The SIG Sauer M400 X-Series SDI boasts a fully ambidextrous lower receiver, including a standard SIG ambi safety, an ambidextrous magazine release, and a right-side bolt catch and bolt drop lever inherited from the Spear LT platform.

What are the barrel specifications for the SIG Sauer M400 X-Series SDI?

The rifle is equipped with a 16-inch barrel made from 4150 steel, featuring button rifling and a mid-length gas system. It also includes a pinned, low-profile gas block.

How does the SIG Sauer M400 X-Series SDI perform in terms of accuracy and reliability?

After approximately 1,000 rounds, the M400 X-Series SDI proved reliable. It achieved sub-MOA five-shot groups with match ammunition, though accuracy degrades as the thin barrel heats up.

What is the expert opinion on the SIG Tango MSR 1-10x scope included with the rifle?

The SIG Tango MSR 1-10x scope is critically reviewed for its poor image quality and chromatic aberration at higher magnifications. Experts suggest alternatives like the Romeo 4XT Pro or a 1-6x scope.

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