The Guntec USA AR-15 Muzzle Device Shim Kit (part no. MB-SHIMKIT) solves the classic clocking problem on a 1/2×28-threaded AR-15, M16, or M4 barrel — getting your flash hider or muzzle brake to land dead vertical or horizontal without over- or under-torquing it. Guntec USA machines the shims from aluminum so you can stack thin and thick pieces behind the muzzle device until it indexes exactly where you want it. This is a cheap, five-minute fix for anyone who’s torqued a brake to spec only to have the ports land off-axis.

Key Specifications

• Built for 1/2×28-threaded AR-15/M16/M4 barrels.
• Includes 4 shims in the kit — one 1.5mm shim and three 0.15mm shims.
• Machined from aluminum for consistent, precise thickness.
• Lets you clock a muzzle device to the correct orientation at final torque.
• Finished in a matte surface to match most muzzle devices.
• Classified as an AR-15 accessory, compatible with standard mil-spec muzzle threads.

Frequently Asked Questions

What thread pitch is this kit for? It’s built for standard 1/2×28 AR-15/M16/M4 muzzle threads.

How many shims are included? Four total — one 1.5mm shim and three 0.15mm shims, so you can mix thicknesses to dial in the exact clocking you need.

What problem does this kit solve? It lets you index a flash hider or muzzle brake to the correct orientation without the device landing off-axis at final torque.

Buy the Guntec USA AR-15 Muzzle Device Shim Kit

A muzzle brake that’s a few degrees off level is a small thing that bugs you every time you look down the barrel, and this shim kit is the cheap fix. Order it from our Lubbock, Texas gun shop and it ships fast to your door, along with more AR-15 parts and accessories.