Upper Receiver Assembly (AR-9, AR-15, and AR-10/LR108)
Step U7: Muzzle Device Installation
Objective: In Step U7 of upper receiver assembly, we will install the muzzle device.
Tools Required
1: Refer to the manufacturer’s instructions and specifications for your muzzle device for the size and type needed. Some muzzle devices come with the required wrench (e.g. VG6 Epsilon).
2: The table below includes the appropriate wrench for our recommended muzzle devices:
| Device | Installation | Type/Flat Span | Recommended Tool |
|---|---|---|---|
| A2 Flash Hider 5.56mm | Crush Washer | 0.750″ | 3/4″ Wrench |
| A2 Flash Hider 7.62mm | Crush Washer | 0.750″ | 3/4″ Wrench |
| Noveske KX3 5.56mm | Crush Washer | 0.750″ | 3/4″ Wrench |
| Precision Armament EFAB 5.56mm | Timing Shims + 20-30 ft.lbs. | 0.750″ | 3/4″ Wrench |
| Precision Armament EFAB 7.62mm | Timing Shims + 20-30 ft.lbs. | 0.750″ | 3/4″ Wrench |
| Precision Armament Hypertap 5.56mm | 20 ft. lbs. | Spanner or 0.828″ | Included (no torque) or Adjustable Crowfoot Wrench |
| Precision Armament Hypertap 6.5mm | 20 ft. lbs. | Spanner | Included (no torque) or Adjustable Crowfoot Wrench |
| Precision Armament Hypertap 7.62mm | 20 ft. lbs. | Spanner | Included (no torque) or Adjustable Crowfoot Wrench |
| Precision Armament Hypertap 9mm | 20 ft. lbs. | Spanner | Included (no torque) or Adjustable Crowfoot Wrench |
| Precision Armament M4-72 5.56mm | Timing Shims +20-30 ft. lbs. | 0.750″ | 3/4″ Wrench |
| Precision Armament M4-72 7.62mm | Timing Shims +20-30 ft. lbs. | 0.750″ | 3/4″ Wrench |
| Precision Armament M11 5.56mm | Timing Shims + 20 ft. lbs. | 0.985″ | Adjustable Crowfoot Wrench |
| Precision Armament M11 6.5mm | Timing Shims + 20 ft. lbs. | 0.985″ | Adjustable Crowfoot Wrench |
| Precision Armament M11 7.62mm | Timing Shims + 20 ft. lbs. | 0.985″ | Adjustable Crowfoot Wrench |
| Surefire 3-Prong SOCOM Flash Hider | Timing Shims + 20-30 ft.lbs. | 3-Prong or 0.750″ | 3-Prong Wrench or 3/4″ Wrench |
| VG6 Epsilon/Epsilon SL 5.56mm | Crush Washer | 3-Prong | Included |
| VG6 Epsilon 7.62mm | Crush Washer | 3-Prong | Included |
| VG6 Epsilon 9mm | Crush Washer | 3-Prong | Included |
| VG6 Gamma/Gamma SL 5.56mm | Crush Washer | 0.750″ | 3/4″ Wrench |
| VG6 Gamma 7.62mm | Crush Washer | 0.750″ | 3/4″ Wrench |
| VG6 Gamma 9mm | Crush Washer | 0.750″ | 3/4″ Wrench |
Components Required
| Quantity | Component |
|---|---|
| 1 | Upper Receiver |
| 1 | Muzzle Device |
| 1 | Crush Washer or Timing Shims1 |
1: Verify the need for a crush washer or timing shims with the table above or the muzzle device manufacturer’s instructions.
Instructions:
Step U7.0: Remove Existing Muzzle Device (replacement/upgrade only)
If you are replacing your muzzle device (or need to remove the muzzle device for any other reason), first ensure the firearm is unloaded.
Remove the muzzle device using the appropriate muzzle device wrench and threading it off of the barrel.
If your muzzle device is pinned/welded, you may drill the pin out using a drill press.
Remove the crush washer or timing shims, as applicable.
If you are reusing the barrel, clean and inspect the barrel threads once the device is removed.
Step U7.1: Determine Timing Shims Required (as applicable)
If using a muzzle device that requires timing shims, determine the combination required to time the device appropriately.
Step U7.2: Apply Rocksett to Barrel Threads (optional)
If desired, you may apply ultra-high temp threadlocker (i.e. Rocksett) to the barrel threads.
Step U7.3: Install the Muzzle Device.
Install the necessary timing shims or crush washer onto the barrel threads.
Thread the muzzle device onto the barrel. Hand tighten.
Step U7.4: Torque the Muzzle Device
Attach the appropriate muzzle device wrench. Set the torque wrench to the value recommended by the muzzle device manufacturer. If you are using an AR armorer’s tool, be sure to Adjust the Torque Setting appropriately.
Torque the muzzle device until the torque drive slips.
Step U7.5: Drill, Pin, and Weld (if applicable)
If you will be pinning and welding your muzzle device (e.g. if you are building a non-SBR on a sub-16″ barrel), proceed to the Pin and Weld tutorial.