Silencer Central
Barrel Threads & How to Attach Your Suppressor
Left: Seekins Havak Element in 6.5 PRC is threaded 5/8-24 and is ready for the Banish 30 Suppressor. The Ruger M77 in 300 WM isn’t threaded and the owner would be sad if his suppressor showed up and had no way of attaching it.

You’ve paid for your suppressor, submitted all your paperwork and tax to the ATF and now you’re waiting. What should you be doing to ensure that you can put rounds downrange the moment your suppressor arrives? 

Depending on the firearms you own you may need to make some modifications, purchase some adapters, or buy some new guns to attach to your suppressor. 

Suppressors are attached to your firearm in one of two ways: 1) they thread directly to the muzzle of your gun or 2) you attach a muzzle device like a brake or flash hider to your barrel that is specifically designed to attach to your suppressor. The second method is called QD, stands for Quick Detach, and is usually slightly faster at attaching the suppressor to your gun than threading your suppressor on and off the barrel. We’ll cover QD attachments more in an upcoming article. Either way though, you need to have your barrel threaded.

For most applications, I prefer option 1, direct thread. I don’t like excess weight out on the end of the barrel and attaching your barrel by direct threading is lighter, simpler, and usually less expensive.

The best way to have your barrel threaded is to buy one already threaded from the factory. Many hunting rifles, most AR-style rifles, and almost all modern precision-style bolt actions come with the muzzle threaded. If you are dealing with a semi auto handgun, many manufacturers now offer tactical models that come with a threaded barrel or you can purchase a drop-in aftermarket barrel for your pistol. 

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The second best way is to have your rifle muzzle threaded. It’s important that this be done by someone competent so that the threads are in line with the bore. This usually requires a lathe to do properly. If the barrel is threaded and not in line with your bore then you can have a bullet potentially hit the inside of your suppressor. This is often referred to as a baffle strike and it can cause major damage to your suppressor.

If you’ve got a barrel that needs to be threaded you can hit up your local gunsmith. Many charge $150 or more to thread a rifle barrel. Silencer Central offers a service where you mail them your gun and they thread it for $99 on a CNC lathe and ship it back to you. I haven’t personally tried the service but it’s certainly an option and should work for you regardless of what state you live in. You can learn more about it here.

Your suppressor will most likely come threaded in one of several common thread sizes and you need to ensure that you have a barrel threaded to match the threads of your suppressor. 

Most Common Rifle Suppressor Thread Sizes

½-28 is the most common thread size for .22 caliber suppressors. So, any caliber that is .223/556 would fit ½-28 threads, including 22 rimfires. It’s also the most common size for muzzle brakes and flash suppressors designed for 22 calibers. The standard muzzle thread size for AR-15s in 223/556 is ½-28. 

⅝-24 is the most common thread size in suppressors for calibers larger than .223 and up to .30 caliber. For example, .243/6mm, .264/6.5, .270/6.8, .284/7mm, .and 308/7.62 would all generally use a ⅝-24 thread size. ⅝-24 is also the most common muzzle brake thread size for 30 caliber barrels. AR-15s chambered in 300 Blackout would use a ⅝-24 thread size as would almost all AR-10s. 

Barrel Threads & How to Attach Your Suppressor
The Henry Lever Action in 38/357 (left) is threaded from the factory 5/8-24 and the Marlin 45-70 (Right) is factory threaded 11/16-24. In this case, you would want the suppressor adapter sold by the company you are buying the suppressor from.

Attaching a Suppressor to a Pistol

Barrel Threads & How to Attach Your Suppressor
The Banish 45 attached to a 9mm pistol with 1/2-28 threads.

Most semi-auto 9mm pistols are threaded ½-28, but there are certainly some exceptions to that so you should check and do your homework so that you have exactly what you need.

Barrel Threads & How to Attach Your Suppressor
An aftermarket threaded barrel was purchased so a suppressor could be added to this S&W M&P 9mm.

The purpose here isn’t to list every single possible thread size. Most pistol suppressors have thread adapters for weird threads available from the suppressor manufacturer. 

I regularly use a 30 caliber suppressor with a ⅝-24 thread on .223 caliber rifles that are threaded ½-28 by using a cheap thread adapter that can be purchased from Brownells, Midway, or even eBay.  Search for Thread Adapter ½-28 to ⅝-24. I’ve bought these for as little as $10. 

Barrel Threads & How to Attach Your Suppressor
AR-15 in 556 with 1/2-28 muzzle threads. The 1/2-28 to 5/8-24 adapters (shown) allow the 30 caliber Banish with 5/8-24 threads to attach to an AR-15 with 1/2-28 threads.

Some hunting rifles with sporter profile barrels don’t have enough metal to thread ⅝-24. As a general rule, your barrel should measure larger than 0.675 in order to safely thread ⅝-24.  If your barrel is under 0.675 I recommend having your barrel threaded 9/16-24 by a competent gunsmith and buying a thread adapter 9/16-24 to ⅝-24 from Brownells. You then red Loctite the thread adapter on and are good to go.

After all the waiting for your suppressor to get out of jail, the last thing you want to happen is to have it not fit your firearm or have the adapter you need out of stock. Now is the time to make sure your firearms will be compatible with your suppressor by getting your barrels threaded or by buying adapters.

Interested in getting a suppressor?  Check out GunsAmerica’s Suppressor Academy. 

About the author: True Pearce is the Managing Editor at GunsAmerica. He’s a competitive shooter, hunter, instructor & attorney. You can see and follow his adventures on Instagram. @true1911 https://www.instagram.com/true1911/

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  • BJ June 28, 2022, 12:15 pm

    It’s been over 5 months getting approval from the ATF form 4, though I went through the new process with Silencer Central. They told me at the ATF, that they are backed up with the new forms.

  • truthsler June 28, 2022, 11:57 am

    not to worry ill make my own.

  • Mark Miller June 13, 2022, 10:24 am

    This is a great primer in an area where there are many misconceptions. If you want a barrel threaded, make sure you have the work done by someone who knows suppressors. I had a local shop ruin a suppressor because of non-concentric threads. The work had to be re-done and the can replaced. Next time, I will use Silencer Central.

  • Gary June 6, 2022, 10:22 am

    When I thread barrels for suppressors, I prefer to have the suppressor here so I can custom fit the threads to the suppressor. The standard class 2 threads we see can be too loose for use in attaching suppressors. The last thing we want is for the suppressor to wiggle at the end of the barrel. I size my threads to start fairly loose, and slowly tighten as is screws on. I want them to be easily turned on by hand to about halfway, then get harder to turn as they go on further. It shouldn’t take a tool to screw them on, but it should take some effort.

    Also, don’t assume those factory threads to be in-line with the bore. I have had to cut off factory threads and re-do them correctly because they were causing baffle strikes on every shot. It is not often, but it does happen.