Over the years, the materials used in the manufacture of moderators have developed, enabling new designs with a change to the placement of the baffle systems

If you are using a .22LR rifle, sound reduction is only required for subsonic ammunition. It is quite straightforward to moderate as it does not have the crack of supersonic ammunition.

The materials used to manufacturers have altered and new designs feature a change to the placement of the baffle systems.

Baffles slow down the advancing hot, expanding gases on detonation/firing, and cool them which lessens the muzzle report.

I have tested a selection of the .22LR moderators that are available to vermin shooters with differing budgets — everything from multi-baffled steel units to the uni/modular aluminium type, as well as those that use synthetic, sound-absorbing materials.

Included in the testing were moderators from some of the old stalwarts, such as MAE, SAK and V-Mach, as well as interesting new designs from the likes of Highland Outdoors and A-Tec.

Testing the performance of sound moderators

I have considered for a long time what is the best way of testing the performance of sound moderators.

Their true performance can be garnered by recording their decibel readings using sound meters from Larson Davis or Brüel & Kjaer — these are professional meters that are able to pick up the entire range of sounds, pressure waves and impulses from a gunshot and, most importantly, the rise time [i.e. have sufficient sensitivity at speed] to capture a true reading.

Most .22LR ammunition gives a reading of 135 decibel (dB) when it is unmoderated while a .308 Win gives a reading of 160dB.

Anything that can reduce the reading by 20-25dB is good. Above that it depends on your hearing and the bullet strike is noisier in any case.

I think having four witnesses is a good way to judge the a moderator’s performance – their reactions say a lot. In any case, professional sound meters can be an expensive hire.

CONCLUSIONS
On any given day, the choice of rifle and ammunition, in addition to the weather conditions, can cause the results of the testing to alter.

This could explain why there is such little variation in the results recorded here.

In all the years that I have been testing sound moderators, no matter how professionally the testing is carried out, their relative performance can be a contentious issue.

The .22LR subsonic round needs only a small amount of retardation of the hot gases to achieve a good result, which does not necessarily equate to the amount of money you spend on the moderator.

For example, while you will be seeking good noise reduction levels, factors such as weight, length, longevity and price will all play a part in your choice.

Any of the following sound moderators would fit the task. To judge which is best for you, look at the dimensions and performance.

DecimeaterJet-zA-TEC CMMSirocco SM11V-machB&T