SilencerCo M13.5x1 LH Piston for 9mm Tilting-Barrel Pistols

The SilencerCo AC26 Piston is the standard-length M13.5x1 LH piston for compatible 9mm pistols using a recoil-operated tilting or unlocking barrel.

The piston threads onto the host pistol barrel and becomes part of the suppressor's Nielsen device / recoil-booster system. That booster assembly allows the barrel and slide to move correctly during the firing cycle while supporting the added mass of the suppressor.

SilencerCo lists AC26 specifically for factory-threaded H&K, SIG and Glock 9mm barrels using the M13.5x1 LH metric thread pattern. Always verify the actual barrel thread before ordering, as manufacturers have used different thread patterns across models and production runs.

AC26: Standard-Length M13.5x1 LH

This listing is specifically for SilencerCo part number AC26:

• Caliber: 9mm
• Thread Pitch: M13.5x1 LH
• Length: Standard

Do not confuse AC26 with AC626, which is SilencerCo's extended-length M13.5x1 LH piston for specific applications such as the SIG MPX with an Osprey and certain Beretta 92FS/M9 metric-barrel setups.

Built for Unlocking-Barrel Pistol Systems

SilencerCo describes its pistons as components of the Nielsen device used on pistols with unlocking barrels.

In a conventional recoil-operated semiautomatic pistol, adding a suppressor directly to the barrel creates enough additional mass that reliable cycling can become difficult. The spring-loaded booster assembly allows the suppressor body to momentarily move independently of the barrel during recoil, helping the pistol complete its normal operating cycle.

The piston is therefore not merely a thread adapter. It is a functional component of the suppressor's recoil system.

Heat-Treated 17-4 Stainless Steel

SilencerCo manufactures its pistons from 17-4 stainless steel and heat-treats them for durability.

The piston experiences repeated mechanical movement, heat and carbon fouling every time the suppressor is fired, so strength and dimensional consistency are important to reliable booster operation and proper barrel engagement.

Compatible SilencerCo Suppressor Families

SilencerCo's current piston guide lists its pistons as compatible with the following suppressor families when the suppressor is configured with the appropriate piston housing:

• Spectre 9
• Omega K Series
• Hybrid 46
• Hybrid 46M
• Omega 36M
• Octane Series
• Osprey Series

Some suppressors require an additional piston-mount housing before a piston can be installed. For example, modular rifle / pistol suppressors such as the Hybrid 46M and Omega 36M use the appropriate Charlie piston-mount configuration, while other suppressor families use their own piston housings.

Verify the suppressor model and mounting configuration before assuming the piston alone completes the installation.

Metric Pistons Shoulder at the Barrel Nose

SilencerCo's metric centerfire pistol thread specification is different from the conventional square-shoulder arrangement commonly encountered with many inch-pattern barrel threads.

SilencerCo specifies that its metric centerfire pistol accessories, including the M13.5x1 LH AC26 piston, shoulder against the nose of the barrel threads. Correct barrel geometry is therefore important for proper seating and alignment.

This is another reason to verify that the threaded barrel was manufactured to the correct suppressor-ready specification rather than relying only on the thread-pitch marking.

M13.5x1 LH Is a Left-Hand Metric Thread

The LH designation means the piston uses a left-hand thread. Installation and removal therefore turn in the opposite direction from a conventional right-hand thread.

M13.5x1 LH has historically been common on European-pattern 9mm threaded barrels and has been used on factory suppressor-ready pistols from manufacturers including H&K, SIG and Glock.

Not for Rifle-Caliber Use

SilencerCo specifically warns that its pistol pistons are intended for pistol-caliber applications. They should not be used as a mounting method for rifle cartridges such as 5.56 NATO.

The piston and booster assembly are designed around the operating requirements of handgun suppressor systems, not rifle-pressure mounting applications.

Fixed Barrels Require a Different Configuration

On a fixed-barrel firearm, the booster normally does not need to reciprocate. SilencerCo specifies use of a Fixed Barrel Spacer in compatible piston-equipped systems when the same suppressor is used on an appropriate fixed-barrel pistol-caliber host.

Do not treat a tilting-barrel booster setup and a fixed-barrel setup as interchangeable without configuring the suppressor correctly for the host firearm.

Swap Pistons to Move a Suppressor Between Hosts

One advantage of SilencerCo's piston system is that the piston can be changed to match different compatible barrel threads.

If two pistols use different muzzle threads but the suppressor supports both, the shooter can install the appropriate piston instead of replacing the entire suppressor mounting system.

For a factory-threaded 9mm host using M13.5x1 LH, AC26 is SilencerCo's standard-length piston for that interface.

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SilencerCo | SilencerCo Suppressor Accessories | Silencers & Suppressors