Good morning everyone and welcome back to TFB’s Silencer Saturday series brought to you by Yankee Hill Machine, manufacturers of the YHM Turbo 5.56 and YHM Resonator R2 rifle suppressors. Last week we sat down with the AMTAC Mantis and discussed the pros and cons of over-the-barrel reflex style suppressors. This week we take a look one of the most frequently asked questions when a shooter is shopping for an AR-15 suppressor – is a 5.56mm can quieter than a 7.62mm can? But the bigger issue is why James Reeves got it wrong.
AR-15 Suppressors @ TFB
- Best Suppressor for the AR-15? [.223 versus .308 Cans]
- SILENCER SATURDAY #150: .223/5.56 Cans -Three AR15 Suppressors
- SILENCER SATURDAY #138: Picking The Best 5.56mm AR15 Suppressor For You
Since the AR-15 is now one of the most popular firearms in history, it makes sense that suppressors for the platform also top the list of what gun shooters decide to suppress first. Truly green buyers who walk into a local gun shop without doing any research may believe that they can only pick from the 5.56mm options to suppress their AR. Those who have done a bit of comparison shopping may know that either a .223 or .308 caliber silencer can be used on an AR-15, but may be unsure of which one will give them the best performance. And veteran suppressor owners will have already answered the above question and are looking to suppress a specific AR-15 host with a new can. The question is a bit more complex than just bullet size versus bore size.
Bore Diameter, Baffle Design and Back Pressure
Contrary to what some internet heroes will lead you to believe, an excellent suppressor is more than just a tube with some discs sandwiched between two end caps. A good deal of engineering goes into fluid dynamics, pressure ratings, length and diameter calculations, and more. Let’s take a look at some of the top challenges that designers face:
- Baffle Design – Not all rounds and hosts are created equal, meaning that good baffle designs can and will be different depending on whether the host will be shooting supersonic or subsonic ammunition. Suppressors designed for 5.56mm ammunition should be tailored for supersonic arounds. On the other hand, suppressors designed for 300BLK ammunition need to be able to handle both supersonic and subsonic ammunition efficiently. This is part of the reason that some manufacturers have multiple models for the same caliber. The Dead Air Sandman and the Dead Air Nomad are good examples – the Sandman is a heavy duty suppressor meant mostly for supersonic use and the Nomad is made mostly for subsonic use (it still performs well on both). As I am not an engineer, I won’t attempt to discuss what makes a good subsonic baffle versus a supersonic baffle.
- Length – This characteristic is more than just an attempt to create internal volume. Baffle geometery along with overall length will determine how many baffles will fit inside the tube and the spacing between each one. One thing to keep in mind for supersonic rifle suppressors is that length trumps diameter when it comes to creating internal volume. Hoop stress/strength (force over area exerted circumferentially in both directions on every particle in the cylinder wall) is another reason we don’t see many supersonic rifle suppressors with diameters greater than 1.4-1.5 inches.
- Bore Diameter – In an absolutely perfect world where tolerances are zero, baffle designs handle pressures perfectly and host/ammunition selection are hyper-controlled, the smaller the bore diameter of the silencer, the quieter the shot. Squeezing a bullet through a tight bore will mean less expanding/exploding gasses escaping around the bullet and out into the outside atmosphere to be heard by the shooter. However, we live in an imperfect world and tolerances must be factored for host and ammunition variability. And lets not forget user error.
- Back Pressure – Last, but certainly not least, a quality suppressor will be designed around a specific host action. All of the attributes discussed above will play into how the host is able to adapt to increased muzzle pressure and where it is ultimately directed. A closed action, like a bolt action rifle, doesn’t need to worry about back pressure because the action is opened seconds after the bullet leaves the bore. A semiautomatic rifle, however, starts opening almost immediately after the bullet is traveling down the barrel. Direct impingement AR-15 rifles can be susceptible to back pressure, where the increased pressure inside of the suppressor is forced back down the barrel and gas tube, increasing cyclic rates and spraying gas and particulate matter back at the shooter. At times, like you see in James’s video below, shooting an AR with a suppressor means the decibel levels can be higher at the action than they are at the muzzle.
Circling back to the topic at hand, all of these discussions are important because it means it is incredibly difficult to determine if a 5.56mm or 7.62mm suppressor will be quieter on an AR-15 host. Bore diameter will be a factor, but there is a lot more that ultimately goes into the overall determination of “quieter”.
SILENCER SATURDAY #178: James Reeves Picks The Wrong AR-15 Suppressor
Clickbait headline aside, while James was wrong in thinking that the 7.62mm silencer would be the quieter of the two models shot on this occasion, his actual thinking is solid. Larger caliber suppressors are generally longer with more baffles and may even be slightly larger in diameter. Coupled with the fact that the 36M can be used on multiple hosts and still sounds great, his initial assessment, I believe is actually the correct one. First, and even second and third, time buyers should lean towards a more adaptable suppressors that will work on a few different semiautomatic hosts when it comes to supersonic rifle rounds. Let’s face it, even with the best suppressor, these shots will still be loud, requiring hearing protection. Closed action hosts and/or subsonic ammo will change this analysis completely.
Anyway, watch the video and let me know what you think. It’s well done and entertaining.
Have a great weekend and we’ll see you back here next week for TFB’s Silencer Saturday.
Suppressors in this video:
- Full-auto rated
- Sound: 134 dB (5.56mm)
- Weight: 16.7 ounces
- Length: 6.4”–7.3”
- Build materials: stainless steel; Stellite
- MSRP: $864
- Silencer Shop: $689
- Full-auto rated!
- Magnum rated
- Length (Long): 7.625 in
- Length (Short): 5.75 in
- Weight (Long): 16.3 oz
- Weight (Short): 13.6 oz
- Build Material: 17-4 Stainless Steel
- Finish: Cerakote
- Compatible with SilencerCo Charlie and Saker accessories
- MSRP: $1187
- SilencerShop: $949
In this episode of TFBTV filmed at Silencer Co in Salt Lake City, James Reeves and Austin R. from The Firearm Blog go to Silencer Co’s lab to answer the question: “Which silencer do I get for my AR-15? A .223 or a .308 can?” This is a difficult question because .308 cans are more versatile and can be used with more calibers including .300 Blackout. On the other hand, .223 cans are lighter, smaller, and usually less expensive. In this video, we have a blind panel compare the sound from each without knowing which is which, and asking what they think about .223 versus .308 cans. After the guys give their opinions, we hook the AR-15 up to a sound meter to see which one is actually quieter. The results may surprise you.
- 0:00 Intro
- 1:21 The Competitors
- 3:24 The Rules
- 4:07 The Competition Begins
- 6:45 The Guesses
- 8:32 The Big Reveal
- 8:58 Meter Testing
- 11:18 Summary, Recommendations, and Conclusion
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Silencer Saturday is Sponsored by Yankee Hill Machine