Silencers with semiautomatic pistols

General information on the use of silencers with semiautomatic pistols with a locked breech design.

The key question is: “Will my pistol be functioning reliably with a silencer and subsonic ammunition?”

The answer is: “It should. But only when the correct ammunition is used.”

Not all ammunition available in our market marked as SUBSONIC will guarantee a reliable function of the combination of a firearm, silencer and possibly other accessories.

We would like to use this opportunity to share with you our experience acquired during the time spent designing silencers.

The most complicated and demanding from the user point of view are silencers containing a pulse device designed for use with locked breech semiautomatic pistols. In order to be able to reliably utilize this type of firearms and silencers, it is useful to know some basic information.

Semiautomatic pistols with the breech mechanism locked by a barrel swing or barrel rotation are not primarily designed to be fired with a silencer or other “weight” on the barrel. Therefore, any additional load on the barrel or slide will affect the operation of this system to a varying degree. The choice of ammunition with sufficient performance is therefore essential for reliable operation of the firearm. On some firearm models, it is necessary to replace the standard recoil spring with a weaker or stronger one for reliable operation with a silencer.


In general it can be said that the best option in terms of reliable functioning of a semiautomatic firearm with a silencer is to use ammunition with the heaviest bullet possible and with the muzzle velocity just below the speed of sound (approximately 330 m/s). When talking about the most common caliber – the 9 mm Luger – subsonic cartridges mostly use bullets with weights from 140 gr to 158 gr.

Unfortunately, even the use of factory-produced subsonic ammunition will not always guarantee a reliable self-loading function of your firearm. The packaging of your ammunition always contains information on the bullet weight, but it is often the case that it lacks information on muzzle velocity (V0). And if it does provide this info, it almost never states the barrel length this velocity applies to. It is clear that velocity value measured on a 20” ballistic barrel will be significantly higher than the value measured on a pistol with a 4” barrel. Another variable is the quality of production. Even factory-produced ammunition can show variations in muzzle velocity in cartridges of the same type and batch of up to several tens of m/s.

Therefore, it is of utmost importance to test which ammunition works for your firearm and silencer combination the best. Currently the best subsonic cartridges available in the Czech market are FIOCCHI 9mm SUBSONIC with a 158gr bullet.

Due to the limited choice and the unstable quality of factory-produced ammunition available in our market, the best option seems to be reloaded ammunition.

To facilitate reloading, the following table shows combinations of bullet weights and muzzle velocities for 9 mm Luger subsonic ammunition with which an overwhelming majority of semiautomatic pistols should function reliably.


Bullet weightMuzzle velocity for a 4″ to 5″ barrel
We strongly recommend using full-metal jacket or metal plated bullets. The use of pure lead bullets leads to significant fouling of the firearm and silencer mechanisms, and they can cause functional defects.


Dozens of pistol models from leading global manufacturers passed through our hands during functional testing of our silencers. If we were to generalize their suitability for use with a silencer, we would state the following:

It mostly applies that the longer the barrel, the more reliable the function with the same powder charge is. Therefore, models with standard duty size are usually more suited for use with a silencer and subsonic ammunition than the same pistols in the Compact or Subcompact size.

Another thing that has impact on reliability is the use of a red dot sight on the slide of a semiautomatic pistol. The heavier the red dot sight, the higher the impact on reliability is when combined with a silencer and subsonic ammunition.

Some models of semiautomatic pistols do not function reliably with a silencer even when the most powerful subsonic ammunition is used, and, therefore, their reliable function must be ensured by using a different recoil spring. Whether a stronger or weaker spring should be used depends on the design of the specific pistol model. Some manufacturers supply their “suppressor ready” pistol models with two or even more recoil springs.

CAUTION! If you use a pistol with standard “supersonic” ammunition, refrain from using the weaker spring designed for subsonic ammunition when using a silencer. Otherwise you could substantially reduce the service life of your firearm.
Sectional drawing of the pulse device used in G.I.S. silencers