Suppressor Types and Thread Pitches

What is inside one

A suppressor is a pressure vessel with obstacles in it. Propellant gas leaves the muzzle at very high pressure, and the can gives that gas somewhere to expand, slow down, and cool before it reaches open air. Less pressure differential at the exit means less noise.

The first chamber behind the threads does the most work, which is why it is the largest. Everything after it is refinement. Two cans of the same length and material can perform very differently based on baffle shape alone.

The four categories

Rimfire

Built for .22 LR, .17 HMR and similar. The cheapest entry point and, in relative terms, the most dramatic sound reduction you will experience, because a subsonic .22 through a good can is genuinely quiet rather than merely hearing-safe.

The distinguishing feature is that most rimfire cans come apart. Rimfire ammunition is filthy, and lead and unburnt powder build up fast. Rimfire suppressors are user-serviceable by design. Centerfire cans generally are not, and should not be opened.

Pistol

9mm through .45 ACP. The complication here is that most tilting-barrel pistols will not cycle reliably with weight hanging off the muzzle, so pistol cans typically use a booster, also called a Nielsen device or a linear inertial decoupler. It lets the barrel tilt and unlock normally.

If you plan to run the same can on a pistol-caliber carbine, which has a fixed barrel, you generally swap the booster for a fixed-barrel spacer. Ask before you buy if that matters to you.

Rifle

Centerfire rifle cans handle far higher pressure and heat, and they are built accordingly, usually fully welded stainless, Inconel or titanium. A .30 caliber can will run smaller calibers such as 5.56 and 6mm variants, which is why many people buy .30 first.

Going the other direction is not optional. Do not put a projectile through a bore too small for it. That is a baffle strike, and it destroys the can and possibly the rifle.

Multi-caliber

Rated across several platforms. The flexibility is real, and so is the compromise: a can sized for .30 is larger and heavier than a dedicated 5.56 can, and it will not be as quiet on 5.56 as a purpose-built one.

For a first purchase covering several rifles, this is usually the right answer anyway. The tax is $0 now, but the wait and the paperwork are still per item.

Direct thread or quick detach

Direct thread screws straight onto the barrel. Fewer parts, less weight, less to go wrong, lowest cost, best concentricity. The trade is that moving it between guns means unscrewing a hot suppressor, and thread pitches have to match.

Quick detach uses a muzzle device on each host and a matching mount on the can. More expensive and slightly heavier, but you can move one suppressor across several rifles in seconds. Most people with more than two hosts end up here.

Budget for the mount. A suppressor with no way to attach it to your rifle is an expensive paperweight, and QD muzzle devices run roughly $70 to $300 each depending on the system.

Thread pitch by platform

Thread pitch is written as diameter by threads per inch, so 1/2x28 means a half-inch diameter with 28 threads per inch. Metric pitches are written as diameter by millimeters per thread, sometimes with LH for left-hand.

Treat that as a starting point, not gospel. Manufacturers deviate, imports vary, and left-hand threads catch people out. The only reliable answer for your specific gun comes from the manufacturer of that gun.

Matching pitch is not the same as fitting

This is the part that gets skipped and it is the expensive part. Three things beyond pitch decide whether a can mounts safely.

The shoulder. The suppressor or mount has to seat squarely against a flat shoulder on the barrel. A thread that runs out into a radius rather than a clean shoulder will not index reliably, and a can that is not square to the bore is a baffle strike waiting to happen.

Concentricity. Threads cut off-axis point the can slightly away from the bore. It can look perfect and still be wrong. This is why threading is worth paying a competent gunsmith for.

Bore diameter. The can has to be rated for the caliber going through it, and for the barrel length and rate of fire you intend. A short barrel raises pressure at the muzzle, and some cans are not rated below a given length.

If you are having a barrel threaded, tell the shop which suppressor and which mount you intend to use before they cut anything.

General information. Confirm thread specifications and caliber ratings with the manufacturers of your firearm and your suppressor before purchase or installation.