AB Prototype M400 Barrel Nut Wrench

AB Prototype

Was: $49.99
Now: $34.99
(5 reviews) Write a Review
SKU:
ABP001
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Barrel Nut Wrench for SIG M400 Tread Handguard

This the AB Prototype, LLC. custom laser-cut wrench for the SIG Sauer M400 Tread Barrel Nut. It will work for removing and installing the barrel nut of the SIG M400 Tread free-float handguard. Laser-cut 3/16" steel and nitride coated for durability. Tougher than the thin factory wrenches. Fits snug to barrel nut, laser engraved with the AB Prototype logo. 

Includes: 1 AB Prototype, LLC. SIG M400 barrel nut wrench. Requires 1/2" torque wrench (not included). FOR BARRELS NUTS 1.37" OD.

Handguard or parts are NOT INCLUDED. TOOLS CANNOT BE RETURNED.

See our quality tools: HERE

5 Reviews Hide Reviews Show Reviews

  • 5
    Money Well Spent!!

    Posted by Not my real name on Mar 9th 2026

    Don’t even waste time with Sig’s barrel nut wrench. This one’s actually built to remove a barrel. No twisting bending tweaking, it’s tough and worth every penny!

  • 5
    M400 Barrel Nut Wrench

    Posted by T on Feb 16th 2026

    Needed it for about 10 seconds, but it works. Much more substantial than the official Sig tool, so great!

  • 5
    M400 Barrel Wrench

    Posted by Phil on Nov 7th 2024

    Perfect quality and extremely fast delivery.

  • 5
    M400 Barrel nut wrench

    Posted by Dave on Jun 25th 2024

    Solid tool and much better than the factory version in my opinion.

  • 5
    M400 Tread Barrel Nut Wrench

    Posted by Doug Woodbeck on Oct 10th 2021

    Was helping a friend who got a live round jammed in the chamber of his Sig Sauer Tread AR-15. Couldn’t get the round out, so he decided to just put on a new barrel. Unbeknownst to us, Sig uses a proprietary barrel nut; of which none of my barrel nut wrenches fit. So, I ordered the AB Prototype barrel nut wrench for the M400. It only took a few days to arrive, and it fit and worked like a dream. The old barrel was off, and the new one on, in just a few minutes. You can’t ask for a better wrench than the one from AB Prototype.