35 decibels down

 YHM’s Sound Suppression System makes good on a tactical promise…"We could communicate while shooting"

 Lindsey Bertomen

I tested YHM’s Q.D. Stainless 7.62 Sound Suppression System (YHM-3300-A) and the 5.56 Q.D. SS (3500 A). YHM (Yankee Hill Machine Co. Inc.) makes several different types of suppression systems, in three different materials: steel, titanium and Inconel, a high performance alloy (although neither of these particular suppressors contain Iconel). The models I tested have a unique QD (Quick Detachable) mounting system.

All YHM Sound Suppression Systems are rated for full auto. Just to be clear, not all suppression products can handle full auto, or the temperature extremes associated with shooting and cooling.

YHM makes two different types of mount systems for this type of suppressor: Thread on or QD. I prefer the QD mount for the carbine. This product allows for easy maintenance and inspection.

I would not have been able to test suppressors at all without the help of my friends at Oakdale (California) Police, Rock Anderson and Max Messina. It was not just because I live in an area where it is difficult to get guns, let alone suppressors…these guys have more technical experience with this type of product than I’ll ever have. Not only that, but we were practically looking through our pockets to see who had enough ammunition for the test. You see, because of the political climate [It seems]… having enough ammunition for the good guys to practice on their own is a significant challenge.

The most notable feature on the YHM QD suppressor line is the fact that the mount—not the muffler part—has all the moving parts. Most suppressor products have some sort of torque limiting device that prevents the user from over-tightening the suppressor on the muzzle. Without it, over-torqueing the product could cause thread failure, misalignment and eventually a very dangerous condition for the user.

YHM has recently improved their Phantom 5.56 Q.D. Flash Hider for sound suppressors, which includes carbon scrapers for inside the can. It also accepts the 7.62 (30-caliber) suppressors, which can result in a cost reduction for agencies who purchase the 30-caliber suppressor for both applications. This works, by the way. The best part about it? The smaller caliber cans don’t fit on the larger QD mounts, preventing major mishaps.

Any agency armorer who has gone through the process of acquiring a suppressor for their department will appreciate this: the part that will likely need replacement from wear and tear and abuse is not the restricted item.

Those of us in law enforcement recognize the implications here: it takes paperwork to send it back to the manufacturer. It takes paperwork to return it to the agency. Anyone who has had a similar experience should know that the turnaround can be several weeks, simply because of BATF eat regulations. YHM persevered here, making the most likely replaced or serviced item a non-regulated device. Brown Santa can deliver the QD mount. The suppressor stays with the agency.

The other strength in the YHM design is the fact that the suppressor itself will likely never need any type of refurbishment. In fact, I asked Matt Hebert of YHM if it was true that soaking them in oil (use what the manufacturer recommends), then draining the product, works. Hebert told me they are that simple. Anderson told me that draining then blowing out the suppressor works well, and added that the carbine should be stored muzzle-down, preventing drainage into the action.

YHM is one of the oldest AR-15 manufacturers in the business. They have been around since 1951 and their experience for precision manufacturing tolerances is well known. Funny, YHM’s biggest competitors are also their customers. That is, YHM’s parts are used in many name-brand AR-15 builds. I should know, my own favorite AR-15 builds use YHM parts.

Suppressors get hot when used. They are basically specialized mufflers, similar in design to auto mufflers, which they actually predate. The principle is simple: an incremental bleeding of gases, rather than a quick release, dissipates the sound also.

If one looks at the photos, one will notice that a suppressor produces a little gas and backpressure. Left-handed users who didn’t invest in a left-handed Stag Arms upper will really notice this. The gas blows back at the shooter.

What mitigates the gas condition? First, the PRI (Precision Reflex Inc.) M84 Gas Buster Charging Handle is a good investment. I recommend the M84 Military Big Latch model. This product works well with any AR-15 product, let alone a suppressed one; I know some may suggest a piston upper. The piston advantage is interesting from an engineering standpoint, but there is nothing wrong with the inherent reliability of the impinged system.

Suppressors are not completely silent; one can expect to experience about a 30-35 decibel reduction out of a good 5.56-caliber product. The 35-decibel reduction from the YHM 3500s brought the noise down to a level that gives the intended tactical advantage for law enforcement officers: we could communicate while shooting.

Suppressors generally change the point of impact between when it is mounted and dismounted. This is simply a difference in the harmonic of the barrel with the extra weight and the placement of the weight. The best way to accommodate for this shift is to always shoot with the product mounted and treat it like an integral part of the carbine.

It is preferable to at least have a point of impact shift to be vertical, although I have seen some products shift horizontal. The YHM 3500 A shifted 1 foot at 50 yards with the suppressor off. Rock Anderson told me that he could totally live with that and proceeded to demonstrate target engagement, on or off. The accuracy was predictable, which is key here. I guess it didn’t hurt that this product was on a Noveske barrel.

How did the YHM 3500 A shoot? The balance of the added 20 ounces on the muzzle really improved the handling. Anderson recommended a 10.5-inch barrel length here, which worked for the carbine length gas system and this product.

The diameter of the product did not get in the way of optics and, most importantly, fit in standard diameter forends.

The YHM-3300-A has a new big brother, the YHM-3300-Ti, which is now a titanium product which offers 32db reduction. I found the YHM-300-A to be the perfect product for 30-caliber cartridges like the 300 Blackout.

Concentricity is critical in a QD mount, and the way to test it is to mount and dismount a suppressor, checking for point of impact shift. The YHM-3300A mounts solidly on the muzzle every time. The QD mount screws in, then ratchets when it reaches the torque limit. The ratchet is important. They get hot. A user with gloves (folks, you’ll forget gloves only once, I promise) will touch the hot can for only seconds at a time. This causes the user to not be able to estimate the amount they tighten the product, and can cause over-tightening.

YHM is one of my favorite AR-15 product manufacturers; they are well known for AR-15 replacement parts, and their complete upper and complete builds are top notch. I’ll add to that their suppressor systems are some of the best products I have ever tested.