Step U5: Muzzle Device Installation
Objective: In Step U5 of upper receiver assembly, we will install the muzzle device.
Tools Required
1: Use grease for any muzzle device that uses a crush washer or a lock nut. For more information visit our dedicated Lubrication and Lock and Lube articles.
2: Use ultra-high temp thread locker on devices that use timing shims. For more information visit our dedicated Thread Locker and Lock and Lube articles.
3: 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, Precision Armament HYPERTAP).
4: 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 | Timing Nut + 20 ft. lbs. | Spanner or 0.828″ | Included (no torque) or Adjustable Crowfoot Wrench |
| Precision Armament Hypertap 6.5mm | Timing Nut + 20 ft. lbs. | Spanner | Included (no torque) or Adjustable Crowfoot Wrench |
| Precision Armament Hypertap 7.62mm | Timing Nut + 20 ft. lbs. | Spanner | Included (no torque) or Adjustable Crowfoot Wrench |
| Precision Armament Hypertap 9mm | Timing Nut + 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
Secure the Upper
Install the action rod into the upper receiver per the manufacturer’s instructions.
Secure the action rod in the bench vice with the upper receiver right-side-up.
Step U5.0: 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 a breaker bar.
Do NOT use a torque wrench to loosen a tightened muzzle device. Excessive reverse torque may damage some torque drives.
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.
If any threads are damaged, you can use an appropriate threading die (typically either 1/2″ x 28 tpi or 5/8″ x 24 tpi) to clean and align the threads.
Step U5.1: 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 U5.2a: “Wet” the Barrel Threads
For muzzle devices using a lock nut or crush washer, install the crush washer (as applicable; do NOT reuse crush washers) and apply ultra-high temp grease (e.g. Molykote G Rapid Plus Paste) to the muzzle threads.
For muzzle devices using timing shims, install the required timing shims and apply several drops of ultra-high temp thread locker (i.e. Rocksett) to the muzzle threads.
Step U5.3: Install the Muzzle Device.
Crush washers may technically be oriented either way, but we recommend orienting it with the tapered end toward the rear (against the shoulder of the barrel to ensure positive contact with the barrel).
Step U5.4: 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.
For muzzle devices using a crush washer, torque the device to 10 ft. lbs. This is the minimum torque required. Continue to torque until the device is properly aligned. Note that we do not recommend exceeding 20 ft. lbs. of torque. Never exceed 25 ft. lbs., as this will constrict the bore and affect accuracy.
For muzzle devices using timing shims, torque the muzzle device until the torque limit recommended by the muzzle device manufacturer is reached. Note that we do not recommend exceeding 20 ft. lbs. of torque. Never exceed 25 ft. lbs., as this will constrict the bore and affect accuracy.
You can verify the correct alignment of most muzzle devices using two 12″ sections of 1/8″ drill rod or two bamboo skewers. Balance one rod in a the Picatinny slot on the upper receiver and feed the other rod through the muzzle device (such that it would be horizontal when the muzzle device is properly timed). Tighten the muzzle device until the angles of both rods appear aligned when viewed from the muzzle.
Step U5.5: 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), drill, pin, and weld the device.
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