Frequently Asked Questions

General FAQ's

Do you ship Internationally?

Yes, we accept and ship online orders for customers of the United States as well as Canada.  All other international inquiries may email us at to discuss ordering options.

How do I receive Dealer/Military/LEO pricing on my internet orders?

If you are approved for discount pricing and you have an online account please send us an email and we would be happy to adjust your account to reflect your discount at final checkout. Then all future purchases can be made fast and easy online!

Can I place my order by phone?

Yes, please call us toll free at 1-800-724-3802. We are open Monday thru Friday, 8:00am to 5:00pm EST. We will be happy to take your order over the phone and ship it out right away.

May I place an order by Check or Money Order?

Absolutely! If you do not wish to purchase via credit card you may call our toll free number to place your order and let our sales representative know you will be mailing in a check or money order for the order total. Or you may click and print our mail order form below and send it in with your payment.

Mail Order Form

Muzzle Brake FAQ's

What barrel threads are required to install a muzzle brake?

To view required barrel thread spec’s please see our Technical Resources page.

Can I purchase a muzzle brake with custom threads or bore?

Unfortunately, as the designers and a large production CNC shop it is only feasible for us to manufacture muzzle devices in the thread and bore sizes we offer. However, many customers have worked with a qualified gunsmith to re-bore or re-thread our brakes (or their barrel) to fit their needs. Click HERE to see a list of recommended gunsmiths who are also Precision Armament dealers.

Which muzzle devices require the Accu-Washer™ System for indexing?

We recommend the following:

  • M4-72 5.56 Compensator: 1/2-28 Accu-Washer™ System (A02119)
  • M4-72 7.62 Compensator: 5/8-24 Accu-Washer™ System (A02219)
  • M4-72 AK47 Compensator: None required
  • AFAB 5.56 Hybrid: 1/2-28 Accu-Washer™ System (A02119)
  • EFAB 5.56 Hybrid: 1/2-28 Accu-Washer™ System (A02119)
  • EFAB 7.62 Hybrid: 5/8-24 Accu-Washer™ System (A02219)
  • M11 5.56 Muzzle Brake: 1/2-28 Accu-Washer™ System (A02119)
  • M11 7.62 Muzzle Brake: 5/8-24 Accu-Washer™ System (A02219)
  • M41 Muzzle Brake: None required

Alternatively, you can use a peel washer or other multi-shim system for indexing either one. We do not recommend using crush washers.

Can the M11/M41 brake be modified to fit larger diameter barrels?

Yes, if performed by a qualified gunsmith. Metal can be machined off the back of the brake where it tapers to meet the barrel to make it larger. The M11 can be enlarged up to .900″ and the M41 can be enlarged up to 1.000″ before machining into the baffle reliefs. We cannot accept returns once the brake has been modified.

What is the appearance of the matte stainless finish muzzle brakes?

Our matte stainless (“in-the-white”) muzzle brake models are blasted in a fine aluminum oxide. This gives them a satin/matte low luster (or non-reflective) stainless finish. As with any finish, stainless or black, it may not match your barrel exactly. However, our stainless models will blend very well on any matte, low-luster stainless barrel. This is also the same for our stainless Accu-Washers™ and thread adapters.

I see an iridescent appearance on the interior surfaces of my DLC coated brake. Is this normal?

This iridescent or rainbow like effect is a natural occurrence in the DLC (diamond like carbon) coating process. Usually a light application of gun oil will change the luminosity of the surface and cause it to disappear. Although, in most cases, this is rarely ever seen since the interior of any muzzle brake is regularly dosed with powder residue and bore cleaning agents.

What tool should I use to properly install the M41 Severe-Duty Muzzle Brake?

The M41 features five 3/16″ holes around the outside that were designed for use with our M41 spanner wrench. We highly recommend using this wrench to install the brake as it will provide quick, easy, and accurate installation without marring or damaging the brake. As an alternative, the M41 brake can be tightened using a strap-type wrench, pipe wrench, or channel-lock pliers if a durable/soft medium (recommend a strip of leather greater than 1/8″ thick) is used between the brake and wrench jaws for protection. CAUTION: Use of a standard adjustable pin-type spanner wrench may cause deformation to 3/16″ holes due to improper fit.

How do the brakes perform with dust printing?

Dust printing occurs when a muzzle device redirects gases downward stirring up a cloud of “dust” when shooting near the ground. The M4-72 Compensator, M11 Severe-Duty Muzzle Brake and AFAB/EFAB Hybrid Brakes are all designed so they do not redirect gas downward. These brakes will show minimal dust printing in the field. However, the M41 brake vents gas equally in all directions. Therefore, some normal dust printing may occur when shooting the M41 brake near the ground.

Can the bore be enlarged to fit larger caliber rifles?

Yes, if performed by a qualified gunsmith. We recommend enlarging the bore diameter to a minimum of .030″ over the bullet diameter for clearance. The M11 and M41 can be enlarged to fit calibers up .500. This will remove the coating from the bore, however the brakes are stainless steel and will not rust. We cannot accept returns once the brake has been modified.

What is the bore diameter on the M4-72, AFAB, and EFAB Muzzle Brakes?

The bore apertures are cut to the following nominal specifications:

  • M4-72 5.56: 0.283″ nominal bore
  • M4-72 7.62: 0.368″ nominal bore
  • M4-72 AK47: 0.395″ nominal bore
  • AFAB 5.56: 0.257″ nominal bore
  • EFAB 5.56: 0.257″ nominal bore
  • EFAB 7.62: 0.344″ nominal bore

What is the bore diameter on the M11 and M41 Severe-Duty Muzzle Brakes?

The bore apertures are cut to the following nominal specifications (.030″ clearance):

  • 6.5mm (.264 Cal) Model has a 0.294″ bore aperture.
  • 7.62mm (.308 Cal) Model has a 0.338″ bore aperture.
  • 8.6mm (.338 Cal) Model has a 0.368″ bore aperture.
Hybrid Muzzle Brake FAQ's

Does the EFAB provide better flash suppression than the AFAB?

Yes, the EFAB Provides better flash suppression in all barrel lengths. However, the improvement becomes more pronounced as barrel length is reduced. In barrels 14.5-18″ there is only a slight to moderate improvement. In barrels 10.5-14.5″ there is a substantial improvement along with complete suppression of secondary combustion (white flash).

Will the EFAB provide more recoil reduction than the AFAB?

Yes, in ballistic pendulum tests using standard 556mm M-193 NATO Ball Ammunition with barrel lengths ranging from 14.5″ to 10.3″ the EFAB achieved Recoil Kinetic Energy Reductions of 52-60% respectively. This represents approximately 20% better recoil reduction vs. the AFAB.

Does the EFAB produce less Concussion than the AFAB?

In barrel lengths 14.5 and longer concussion is about the same. However in sub 14.5″ barrels the EFAB can completely prevent the component of muzzle blast caused by secondary combustion (this is the bright white flash that is commonly seen in barrels under 14.5″) which is significant component of total muzzle blast energy. Therefore, the EFAB typically produces less concussion than any other hybrid device in sub 14.5″ barrels.

Does the EFAB produce First-Round-Flash (FRF)?

No, in fact the EFAB is the first Hybrid Brake on the market to effectively eliminate FRF. It\’s unique baffle design combined with low internal volume allows nearly all free oxygen to be purged from the interior of the brake before FRF can occur.
FRF is the phenomenon cause when the column of oxygen/air sitting in front of the bullet is compressed and forced into the interior muzzle brake were it quickly mixes with the fuel rich propellant gases following the bullet. This combustible gas mixture then ignites producing a small but brightly visible flash on the first round. Subsequent shots will not produce this flash as long as the bore volume in front of the bullet continues to remain purged with the un-burned propellant gases of the previous shot.

Is erosion a problem when using the EFAB on SBR’s (short barreled rifles)?

No, However with any muzzle device erosion typically starts to become significant when barrel length is reduced to a critical point which is primarily dependant on cartridge expansion ratio (bore volume / case capacity). With .223/556NATO this critical length is usually around 14-16″. The rate of erosion is also considerably affected by firing schedule (ie. semi vs. full-auto) and propellant type as well as the design features and materials incorporated into the muzzle device. To endure the severe conditions present in SBR length barrels the EFAB is constructed from erosion resistant stainless steel and employs an innovative “Erosion Tolerant” internal design which allows it to maintain a stable and effective baffle geometry even while gradually eroding over the duration of its life.

What is the typical service life of the EFAB?

On SBR’s (Short barreled rifles) the service life of the EFAB will typically be at least equal to or greater than the service life of the barrel itself. On SBR’s This can range from as low as a few thousand rounds when subjected to long durations of full-auto fire to well over 25,000 rounds with more conservative firing schedules. On standard length (16″+) barrels, service life is expected to exceed 150,000 rounds. End of service life should be considered reached when the front of exit hole erodes to a diameter 10% larger than factory new condition, although still safe to shoot there will be some performance loss at this point.
During test trials the EFAB’s erosion service life was accelerated by performing long durations of full-auto fire with 10″BBL test guns. At different levels of erosion recoil testing was performed on a Ballistic Pendulum. Test results showed that an exit hole erosion enlargement between 1-5% actually produced a slight improvement in recoil reduction peaking at 3-4% (kinetic energy reduction) with flash suppression performance remaining unaffected. At 5-10% enlargement of the exit hole there was a steady downward trend in recoil performance with a loss of about 5% (kinetic energy reduction) well as a noticeable reduction in flash suppression at the maximum enlargement.

Accu-Washer FAQ's

What should I do if none of the shims work?

Have you found that one shim goes a little past perfect alignment, but the next size bigger wont rotate far enough? Well you’re in the right place! First off, the shim that goes slightly past is definitely not the correct shim to use. The next size bigger is the correct shim to use. Here are some helpful tips to get it to work:

  • First, make sure the threads on your barrel and muzzle device are completely clean and free of all debris. Any contamination can limit the rotation.
  • Next, applying a moly-grease or CLP-type lubricant to the threads on the brake and barrel will provide further rotation for the same torque. We suggest you apply generously, then run the brake on and off the barrel a couple times to work it in, then wipe up any excess. The coefficient of friction between the threads is what limits your rotation, cutting this coefficient in half with grease can give you twice as much rotation. You may also apply some lubricant to each side of the timing shim as there is friction in the works here too.
  • Lastly, a little elbow grease. Since the accu-washer shims are used to adjust your brake in discrete intervals, it is inherent that the torque required for proper alignment will fall in a range. The torque load specified in the instructions is merely the minimum required so your device does not rattle free, however you will need to continue to apply torque beyond this to achieve alignment. Higher torque installs may require holding the rifle in a barrel vise.

Never use Crush Washers for installation?

Crush washers are perfectly acceptable to use on any open aperture muzzle device, such as the standard A2 birdcage flash hider. However, our opinion is they should never be used on any baffle style muzzle device where the clearance hole is only slightly larger than the bullet. Firstly, crush washers come to a knife edge on both mating surfaces – it is likely for this reason that a muzzle device is already misaligned just sitting on the crush washer before it is even torqued down. More importantly, it relies on the principle that the washer will deform uniformly while it is being crushed. This requires that the material is uniform and that you apply a perfectly pure torque load normal to the bore. This is very unlikely (for anyone who has installed one) when you’re putting all your might into the 30-60 ft-lbs of torque they often require. The consequence of this misalignment is a baffle strike at worse and impaired accuracy at best.

We recommend our Accu-Washer Shim System for installation as they alleviate both of these issues providing the highest safety and performance from your device. Also, a peel washer or any precision multi-shim system are also perfectly acceptable methods for aligning your muzzle device.

Also consider that crush washers have the capacity to deform further beyond your install. So, if you happen to hit the muzzle on something with enough force you may permanently angle your device to the side killing your accuracy or worse: rendering the rifle useless.

Why are the Accu-Washer® shims not coated?

The Accu-Washer shims are machined from 416 stainless steel and then oxide blasted to give them a matte, low-luster (or non-reflective) grey finish. They do not require a coating for corrosion resistance and their dark matte grey finish blends well on any stainless or black/blued barrel. In addition, the blasted finish offers excellent adhesion for paint. The exterior of the washer may easily be painted or even blackened with a permanent marker if desired.

Why do I need to purchase all 18 shims in the set?

The position of the threads on every barrel and brake is different and completely random. Therefore it is impossible to know up front which accu-washer shim you will need to correctly index your muzzle device. For this reason we recommend purchasing the complete set. The good news is you will have enough left over shims to index several more devices and you can also buy replacement shims in the event you need a shim you’ve already used.

Why are there 18 shims in the set?

When installing a muzzle device, the device will rotate approximately 20 additional degrees depending on the final tightening torque. Having 18 accu-washer shims in the set allows the user to cover every 20 degree increment across one full rotation (from 0 to 360 degrees).

Why do the 1/2-28 Accu-Washer® shims have a .750″ OD, and the 5/8-24 have a .825″ OD?

There are an unlimited number of different size barrels and contours out there; therefore it is impossible to satisfy every customers specific needs. Both Accu-Washer systems were designed to provide an aesthetically pleasing step from the back of our brakes to a .750″ diameter barrel that is commonly found forward of the gas block on many AR style firearms.

Scope Rail FAQ's

What are the advantages of Tennalum 7068?

The bottom line is Tennalum 7068 has the highest strength-to-weight ratio of all commercially available alloys. It provides an extremely light-weight option for shooters looking to keep weight off their sporting rifles, field rifles, or any tactical rifle without sacrificing strength. The yield strength of Tennalum (~100KSI) exceeds many commonly used scope base steels and it approaches that of pre-hardened 41XX & 400 series stainless steels. However, Tennalum is one third the weight of steel! In fact, it has close to 30% better strength-to-weight advantage over 6Al-4V Grade 5 Titanium.

Do you offer scope rails in cants other than 20 MOA?

At the present time all of our canted scope rails are 20 MOA (except for the shotgun & accessory rails which are zero). However, as we continue to expand our product line we may add rails in higher or zero cants.

What torx wrench do I need for my scope rail?

All Precision Armament scope rails can be installed with a T10 torx wrench.

Why is a wrench not supplied with the Scope Rails?

We figured why increase the retail price and force the customer to buy a wrench they likely already own? And if they buy more than one scope rail from us we would be forcing them to buy it over again. In order to deliver the best possible price, and not force you to purchase another wrench, we did not include one. If you don’t have a T10 torx wrench, we recommend picking up an American made one for a few dollars at any local hardware store. It will be higher quality and less expensive than the cheap wrenches you see included with other rails.

Bolt Knob FAQ's

What machining steps are required to thread my bolt handle for installing a knob?

You can find installation guides on the website under the installation tab on every product page. First, the existing bolt knob needs to be machined down to a cylindrical boss. This is easiest to do by fixturing the bolt body in a mill and using an OD boring tool. It can also be done on a lathe, or it is also possible on a grinder. Next, threads need to be cut on the boss. This can be done in a mill, lathe, or by hand using a threading die. You can also cut them in a lathe using a traditional single point threading tool.

Will Precision Armament thread my bolt handle for installing a knob?

We are sorry, but we do not offer a custom threading service for bolt handles. With the large variety of different bolts out there we would most likely not be very competitively priced anyways. If you don\’t have the required machining capabilities your best option is to look up your local Gunsmith, or click HERE to see our list of recommended gunsmiths.

Thread Adapter FAQ's

Can I purchase a custom thread adapter?

Being a large production CNC shop it is not practical for us to individually manufacture custom thread adapters, therefore we only offer thread adapters in the sizes featured on our website. However, if a custom adaptor is absolutely necessary there are many gunsmiths that will make what you need on a manual lathe for a reasonable price.

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