With sound moderators more popular than ever on sporting rifles, Chris Parkin gives you a run-down of the options
The question of which is the best sound moderator regularly floats around, with a lot of hearsay and subjective opinion inevitably following. Side-by-side testing and full acoustic monitoring to give objective comparisons are hard to organise, but those of us who have shot a lot of them on a wide variety of calibres can still notice a few trends. When I started shooting, sound moderators were in their infancy to sporting shots, and getting a variation for one was not guaranteed, but the ongoing tide of health and safety has overcome this situation. Where a target shooter used to have no chance of getting a mod, it is now common to see them among ‘tactical’ rifle fans, and it seems a foxing rifle is missing something if not modded. Similarly, deer stalking has seen an increase in sound moderator use. This growth in use has led to many new models, styles and thought processes to fulfil our requirements of a mod. It has proven some models excellent, many ok and a few certainly to be avoided. Most importantly, it has brought our real requirements of a moderator to more detailed attention.
Sound moderator needs
So what does a sound moderator do? Most of us think noise attenuation is the primary requirement; recoil reduction is also a factor, but what about durability? It certainly polarises opinion. When you fire a rifle, a fast, hot jet of gas comes bursting out of the muzzle, creating a lot of noise or ‘muzzle blast’. This jet reacts with the atmosphere to create recoil in exactly the same way a jet engine propels a plane.
So for foxing, what are our primary needs? Moderating sound for us as well as for residents within earshot would be the first consideration. Weight is not such a big issue if you are foxing from a vehicle, but durability is certainly key. A foxing rifle is likely to be shot regularly, brought into the house and stored late at night in a hurry, perhaps forgotten until its next outing.
Compare this with a stalking rifle: in a single-shot environment, right or wrong as it is, we can mostly forgive ourselves the odd open-air boom now and again, but mitigating surrounding animals’ reactions to their suddenly immobile companion can be very useful when culling herding deer. In woodland, minimising recoil can help the shooter spot their bullet impact, and when close to heavy cover, it is certainly helpful to have a starting idea of the type of hit and primary injury you have inflicted on a deer you may spend hours tracking. Viewing shot reaction can be extremely valuable.
Lastly, a stalking rifle may well be put away during the day or evening, allowed to warm up to room temperature, be cared for before storage and see a significantly lower round count through its life. So it’s likely to be less of a strain on durability.
A quick note of caution: always take your moderator off the rifle before storage. Condensation forms and will rot a barrel faster than you can click your fingers – be warned.
Having defined specific needs, we can look at the materials and construction style. Moderators can come in Parkerised steel, stainless steel, titanium, as a composite build using aluminium/steel combinations, or an entire carbon fibre unit. Choosing a mod that can be dismantled for cleaning or one that is welded shut and left forever depends on your requirements and its expected lifespan. On a foxing rifle, I would personally use a slightly heavier steel mod. On a stalking rig, an aluminium mod with stainless baffles or baffle centres seems to fit the bill well; although a little lighter in weight, it is the common solution for low round count and strip-down maintenance.
To debunk a few myths, a moderator prevents the jet of gas creating excessive noise and recoil by slowing the pressure release from the muzzle. The jet is made to swirl, expand and diminish before it hits the external atmosphere, and expend the momentum that causes the gun to recoil rearward. This is where volume always helps, but the simple fact is, the gas is going forwards: weight for weight, an end-of-barrel mod will always minimise noise and recoil better than a reflex design. Moderators can get a bit long and wand-like, but there are some seriously compact and low-weight units out there performing well above their stature.
Brake and mod
I dispute the claims of manufacturers who suggest you can call whatever baffles or internal blast arrangements of the mod’s internals a muzzle ‘brake’. A muzzle brake works by expelling gas rapidly, directly to the external atmosphere, thereby reducing the jet directed forward, and expending its energy radially or laterally in complete equilibrium, sometimes rearwards to reverse the jet’s momentum. It won’t work inside a sealed pressure vessel. It might look like a brake and it may cause gas swirling and expansion to depressurise within the tube, but it isn’t a brake – it’s part of a moderator.
For the target or tactical shooters who want a mod for range use, you can get a brake that is screwed to the end of the barrel, working in the usual fashion, and a paired mod will then screw over the brake, giving sound reduction performance. However, make no mistake: the brake has become nothing more than a mounting spigot. It no longer ejects to the atmosphere. Of course, some intelligently designed mods have more than one exit hole up front to allow further gas discharge away from the direct bore line, but these are exits for gases already reduced in pressure, not the initial blast wave. I’d pick a heavy stainless steel mod for durability with great sound suppression – I wouldn’t want to strip it or risk anything being loose internally.
Moderators over time
A solid mod, regardless of material, will eventually rot or burn away. It is exposed to high temperature gases at extreme speeds and pressures that will ‘cut’ the surfaces and remove coatings. Some materials will suffer more than others. A mod that can be dismantled for cleaning won’t have any corrosion flakes tinkling around inside it like a steel mod will. On the other hand, until the day it dies, a welded mod won’t come loose, and any slack in the components of a strippable mod can cause accuracy issues as vibration disturbs the harmonics of your barrel. Most manufacturers suggest checking that the mod is fully tightened when hot and expanding. That way, when cool, it will only get tighter so should cause no problem at either end of the temperature scale. A quick blast of WD40 or such is often recommended but regularly overdone, and the first shot afterwards is a huge blast of white smoke – a terrible smell. I have seen one ‘enthusiastic lubricator’ actually achieve full detonation and a burst mod, thankfully without injury. Chances are, your ‘cold bore shot’ will be off zero too. If you must, be very sparing.
Manufacturing technology has changed significantly, so where we once saw only pressed steel tubes welded together, almost semi-disposable items from military backgrounds, CNC machining has allowed combinations of materials specified to suit individual localised needs within the moderator. For example, you can use a lighter weight aluminium tube and end caps with stainless steel baffles to minimise gas cutting, aluminium baffles with stainless centres to reduce weight, or increase the number of baffles. Baffles are now machined with such intricacy that designers can explore more ideas of fluid dynamics to disperse the jet. Also, as computer modelling becomes more accessible, ideas will evolve further. Modular construction means one moderator can fit several rifles regardless of thread size, or can be adapted to a new rifle. Baffles were once offered in .25 or .30 to cover all sporting calibres, but some are now specific for .17, .20 and .22 to minimise all noise possible. Magnum calibres are catered for with .30. Moderators are available for .338 and .408, even the ‘fifty’, but these are a far cry from the .223 foxing rifle’s needs. The increasing market for moderators and brakes has led to more companies screw-cutting their barrels at the time of manufacture, helpfully avoiding the proof issue that still rears its head occasionally.
Moderators: What’s on the market
ASE Utra, A-Tec and BR-Tuote Reflex
Hardy Sound Moderators
Third Eye Tactical Spartan
Brugger & Thomet
Chris Parkin, freelance shooting journalist