Silencing the 300 AAC Blackout

You have to admit, a silencer makes any rifle cooler – like this SilencerCo Specwar 762 on a Daniel Defense DDM4v5 300 Blackout.

Last time we got into an ammunition geek-fest and talked about the variety of commercial ammo available for the 300 AAC Blackout and the endless tinkering you can do as a reloader for that caliber.

Perhaps even more fun than creating endless varieties of ammunition for the 300 AAC Blackout is shooting it with silencers. With subsonic cartridges, usually those firing 208 grain or heavier projectiles at velocities of 1,000 fps or so, you’ll have some serious quiet. Even when using supersonic 300 AAC Blackout ammunition, you’ll notice a dramatically improved shooting experience. Supersonic rounds will still make that little sonic boom, or crack from the bullet traveling through the air, but the gun shot will sound more like a “whoosh” than a “bang.” Hard to describe in words, it’s a little bit like air brakes on a truck. Know what I mean? Trust me, it’s cool.

Before we get started, let me clear up some terminology. Silencer is the correct legal term, and the one coined by Hiram Percy Maxim back in 1902 when he invented the Maxim Silencer. For a long time, the industry used the term “suppressor,” as it was more descriptive. A silencer doesn’t completely silence after all. Recently, industry folks are moving back to the term “silencer” but you’ll see both terms used interchangeably, and both are technically correct – just in different ways.

Let’s talk about some things to consider when silencing the 300 AAC Blackout and close with a look at a few good silencer options currently on the market.

Even 300 Blackout ammo is cool like these Gemtech 187 grain subsonic rounds.

Your gun will experience “the change.”

More likely than not, your rifle will have a point of impact shift when you add a silencer. In plain english, this simply means that the bullet will hit in a different spot when the silencer is on as compared to when it’s off. Just to be clear, assuming you have a half decent gun, your groups will be consistent with and without a silencer, they’ll just be in different places on the paper. Usually, this is not a huge deal – an inch or two difference.

For example, after shooting a bunch of groups with my Daniel Defense DDM4v5 300 AAC Blackout rifle, I added a SilencerCo / SWR Specwar 762. Measuring the distance between before and after groups, I noticed that my rifle impacted about 1 inch lower and ¾ inches to the right at 50 yards when using the silencer. Your results will almost certainly vary as the “change” results from different barrel harmonics. Every silencer is different and every rifle and barrel combination is different. In any case, this is nothing to get concerned about. You’re not likely to see any dramatic shifts, just be aware that you’ll need to re-zero your optic.

I actually noticed a slight improvement in accuracy when I added the suppressor. While not dramatic, groups using identical ammo in identical conditions shrunk just a bit. Again, your results may vary. Have a little fun testing before and after point of impact and accuracy effects to see how your rifle responds.

Especially if you’re going to shoot lead projectiles, consider a silencer that comes apart for easy cleaning, like this SilencerCo Octane 45.

Things to consider when choosing a silencer for your Blackout rifle.

Ask yourself these questions before choosing a silencer for your Blackout:

Are you going to shoot only subsonic or a combination of super and subsonic ammunition?

If you’re only going to shoot subsonic ammunition, then you have more options. With the lower pressures of subsonic ammo, you can use a 9mm (or larger) pistol silencer, assuming your silencer manufacturer specifies 300 Blackout compatibility. Usually, pistol suppressors are smaller and lighter, so that’s a benefit. Just be sure to never shoot supersonic ammunition through a pistol silencer not rated accordingly.

Are you going to shoot lead projectiles?

If you want to see how much lead gunk can accumulate over time, try a .22 silencer for a while. It’s somewhat incredible. This is not a big deal if you can clean your silencer once in a while. Some models, especially pistol models like the SilencerCo / SWR Octane come apart so you can thoroughly clean the insides.

Is this a major consideration? Not necessarily, but if you’re one to cast your own bullets and such, you might consider a “cleanable” model. Be sure to check with your manufacturer to see if lead voids the warranty or anything harsh like that.

Are you going to use the silencer “full time” on your rifle or take it on and off?

Many silencers, like this SilencerCo Specwar, offer quick attach mounts and compatible muzzle devices, so you can easily move one suppressor to other rifles.

There are two things to consider here.

First, “the change” discussed previously. If your rifle has a significant point of impact shift, then you’ll be faced with the possibility of re-zeroing your scope every time you mount and dismount the silencer.

Second, you’ll want to think about mounting options. Most companies offer quick mount systems where you can buy extra muzzle devices for alternate guns and easily move a silencer back and forth. For example, I use a SilencerCo / SWR Specwar 762 on my Daniel Defense 300 AAC Blackout rifle. The Specwar comes with a muzzle brake inside of the suppressor which mounts to your rifle’s standard barrel threads. The silencer body quick attaches to the muzzle brake or flash suppressor. I bought a second compatible muzzle device for my Rock River Arms LAR-6.8 (a flash suppressor) so I can use the quick mount to easily move the same silencer between rifles. Nearly every manufacturer offers some type of quick mount system, just be sure to order the extra muzzle devices for other guns.

A few silencer options

SilencerCo / SWR Specwar 762

This is the model I’ve selected as my primary for my 300 Blackout rifle. It’s designed to handle full power .308, so 300 Blackout supersonic rounds are no problem. It’s 1.5 inches diameter and weighs 24 ounces. Buy some extra muzzle devices and use it on anything smaller also. I’m currently using mine on a Springfield Armory M1A, 6.8 Remington SPC and the .300 Blackout.

SilencerCo / SWR Octane or SilencerCo Osprey

Both the Octane and Osprey are pistol suppressors, but are fine to use with 300 Blackout subsonic. Consider getting one in .45 ACP. It will still suppress 300 Blackout just fine, but buying a larger bore model gives you the flexibility to mount it on .45, .40, 9mm, 380 ACP and even .22LR pistols. The Octane is a traditional tube design, while the Osprey is oblong, with much of the volume situated below the bore line so sights are less obstructed.

Two SilencerCo models that will work with subsonic 300 Blackout: the Osprey (top) and Octane (bottom)

If you buy a pistol silencer for your Blackout, just be sure to use a fixed mount designed for fixed barrel guns. Many pistol suppressors have “boosters” that help maintain reliability in semi-auto pistols where the barrel moves as part of the recoil cycle. That’ll mess you up on a fixed barrel gun like an AR type 300 Blackout.

GemTech GMT-300BLK

Designed for the 300 AAC Blackout, this one will give you 36 – 39dB of sound reduction. Made from titanium, it’s built to last. Perhaps the most important feature is that it’s cleanable, so if you want to lob those big honkin’ 245-grain lead projectiles downrange, you don’t have to worry (as much) about filling up your expensive silencer with lead residue over time.

Advanced Armament Corp (AAC) 7.62-SDN-6

This model is a bit smaller than AAC’s 7.62 SD, which is optimized for the full size 7.62x51mm NATO round with its extra gas volume. You can still fire 7.62x51mm through it however. AAC rates this model at about 126dB when using 300 AAC Blackout subsonic ammunition.

Two for one! The Daniel Defense DDM4ISR

If you choose a pistol silencer, it may have a pistol and spring assembly, or booster, for use on semi-automatic guns where the barrel moves as part of recoil. When using on a fixed barrel rifle, be sure to use a fixed mount.

If you want to just go out and buy the cat’s meow right off the bat, check out the Daniel Defense DDM4ISR. It’s a nifty solution to minimize the bucks you have to pay the feds for a short barrel Blackout and suppressor. Technically, it’s a carbine length gas system rifle with a 10.3 inch barrel, but it features a permanent integrated silencer. This brings the overall “barrel length” to just over 16 inches. Since it’s permanently attached, the rifle is not considered a short barrel rifle (SBR) and subject to a second $200 BATFE tax stamp. You have to buy one stamp for the integrated suppressor, but that’s all. It’s one sweet honey.

One last thing. While too big a topic to go into here in depth, if you haven’t yet bought a rifle, do a little research on pistol versus carbine length gas systems. .223 / 5.56mm rifles can benefit from “longer” gas system (like the mid-length) as recoil is smoothed out a bit. Shorter length gas systems (pistol and carbine) are more violent on the action because faster gas enters the operating system since the port is closer to that big bang. With 300 Blackout using subsonic ammunition, there’s less gas available to start, and it’s moving at slower speed. As a result, pistol length gas systems can be more reliable. Carbine length gas system guns will work just fine, just be aware they might be more sensitive to ammo types when shooting subsonic. So before you buy, think about your anticipated usage of supersonic versus subsonic and do a little homework. Your silencer manufacturer is a great place to start and they should be able to tell you what type of gun will run best with the model of silencer you have.