Gemtech’s GMT-300BLK Suppressor for 300 Blackout Rifles – Full Review

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The Gemtech GMT-300BLK is made specifically for 300 Blackout rifles.

The Gemtech GMT-300BLK is made specifically for 300 Blackout rifles.

To learn more, visit https://gemtech.com/gmt-300blk.html.

To purchase a Gemtech suppressor on GunsAmerica.com, click this link: https://www.gunsamerica.com/Search.aspx?T=Gemtech.

Suppressing a 300 Blackout rifle presents a unique opportunity because the exact performance attributes are known in advance. Allow me to explain.

If you’re trying to make a generic .30-caliber rifle suppressor, you’ve got to plan for a wide range of potential pressure and general abuse. You don’t know whether, and how frequently, the user will be shooting any type of ammunition all the way up to 300 Win Mag. To get specific, let’s consider the pressures involved with various loads that one might fire through a .30 caliber rifle silencer.

At the low end, you’ll find cartridges like .22LR. That operates at mellow handgun cartridge pressures with a SAAMI maximum of 24,000 psi. Moving up the scale, consider that .30-06 has a maximum SAAMI pressure of 60,000 psi while .300 Winchester Magnum goes up to 64,000 and .308 Winchester tops out at 62,000 psi. On the other hand, 300 Blackout operates at significantly lower pressures, with a SAAMI maximum of 55,000 psi, the same as .223 Remington. Depending on whose numbers you use, the 5.56mm NATO variant tops out at over 62,000 psi.

If you're only going to use it on a 300 Blackout rifle, you don't need a larger and heavier .30 caliber suppressor like the SilencerCo Specwar shown above.

If you’re only going to use it on a 300 Blackout rifle, you don’t need a larger and heavier .30 caliber suppressor like the SilencerCo Specwar shown above.

What’s all this mean? As with .223 rifle suppressors, the top end of the abuse range for a dedicated 300 Blackout can is known, so manufacturers can engineer a silencer as small and light as possible, using materials that will handle a known level of pressure. Being non-caliber specific, most .30 caliber rifle suppressors have to be overbuilt.

The folks at Silencer Shop recently loaned me such a purpose-built suppressor for testing. The Gemtech GMT-300BLK suppressor is, as the name implies, designed specifically for use with the 300 AAC Blackout cartridge. While you can use it on any 300 Blackout rifle with a 7.5-inch or longer barrel, it was really built for short barrel rifle configurations. It’s small and light as far as centerfire rifle silencers go, so it’s a great fit for short, light, and handy carbines. It’s rated for full-auto operation, but the factory manual clarifies “full-auto” as 4-8 round bursts every three to six seconds. Even if you can afford the ammo, don’t make a habit of full magazine dumps in rapid succession.

The interior is machined from a solid hunk of Titanium.

The interior is machined from a solid hunk of Titanium.

The GMT-300BLK is made from Titanium for light weight and strength. When you pick the Gemtech up you can really tell the difference the material makes. I shot it side by side with a SilencerCo SWR Specwar 7.62. The Specwar 762 model weighs in at 24 ounces and is a full nine inches long and 1.5 inches in diameter. The Gemtech GMT-300BLK is just over half the weight at 14 ounces. It’s also 2.3 inches shorter at just 6.7 inches. The diameter is the same at 1.5 inches. The size and weight differences are not just apparent on paper; you feel that reduced weight and size when you mount the Gemtech. Speaking of mounting, it’s a direct-thread only mount with a 5/8×24 tpi pattern. Given its designed use, it’s intended to be a “mount forever” type of suppressor, so the lack of any muzzle devices or quick attach/detach mounting options is irrelevant.

The compact size and light weight are a big deal. The Gemtech is not much over half the weight of this Specwar 762 and over two inches shorter.

The compact size and light weight are a big deal. The Gemtech is not much over half the weight of this Specwar 762 and over two inches shorter.

The GMT-300BLK is user-serviceable for cleaning. That’s a good thing because, while supersonic centerfire rifle models are self-cleaning from the heat and pressure, heavy subsonic use can leave junk like carbon and lead (if you shoot unjacketed bullets) that needs to be removed. The outer tube unscrews from the direct thread mounting base to expose a G-Core baffle. The G-Core system is a single-piece baffle design, so the whole interior is a solid hunk of metal. There’s a nifty trick to remove the outer tube from the baffle stack in the event parts get fused together by carbon deposits. The muzzle has a square opening which is designed to accommodate a 3/8-inch socket wrench so you can apply some leverage with a socket wrench to get the outer tube off if required.

You can use a socket driver to loosen the exterior tube form the G-Core baffle if you need to.

You can use a socket driver to loosen the exterior tube from the G-Core baffle if you need to.

Without a suppressor, the folks at Silencer Shop have established baseline measurements of 208 and 220-grain subsonic 300 Blackout loads from a 9-inch barrel in the 157 to 162-decibel range. Assume the factory suppression numbers are accurate, and that puts the overall sound pressure figures in the 130 dB range when shooting subsonic. Technically, that’s hearing safe, but repetition matters, so if you’re going to be shooting more than a couple of shots, use hearing protection anyway. That’s a good rule to use with any silencer.

To see how the GMT-300BLK compared to a general purpose rifle suppressor, I used it on two different rifles in a side by side comparison with the SilencerCo SWR Specwar 762. I used a Daniel Defense DDM4v5 300 Blackout rifle with a 16-inch barrel and an Aero Precision eight-inch barrel 300 Blackout upper for the test rifles.

The GMT-300BLK made a great addition to this eight-inch Aero Precision upper.

The GMT-300BLK made a great addition to this eight-inch Aero Precision upper.

I shot both subsonic and supersonic ammo from both configurations with a variety of ammo including Sig Sauer 125-grain Match Supersonic, Sig Sauer 220-grain Match Subsonic, and American Eagle 220-grain Suppressor. With both super and subsonic ammo, I noticed a distinct tonal difference between the Specwar and Gemtech suppressors. The larger Specwar produced more of a “hissing whoosh” sound (how’s that for a description?) while the Gemtech exhibited more of a muted “thud.” The Specwar sounded quieter to the naked ear with all gun and ammo combinations, but then again, its supposed to. It’s got a factory rating of 119 dB for subsonic ammunition. With that said, the noise level was fine with both super and subsonic loads, even from the eight-inch short barrel configuration.

With both super and subsonic ammo, I did some quick and dirty testing with and without the Gemtech mounted to see how the point of impact changed, if at all, between suppressed mounted and un-mounted shooting. In the 50-yard bay where I was testing, I could detect no significant difference in the impact point with either of the test guns. Perhaps the light weight offered less interference with the barrel. In any case, I didn’t have to change the zero on my optics when adding the silencer.

The GMT-300BLK uses a direct thread mount only.

The GMT-300BLK uses a direct thread mount only.

The big standout feature of the Gemtech GMT-300BLK is the compact size and amazingly light weight. If you’re going to build a compact 300 Blackout rifle, this makes a great addition. It’ll keep the overall length acceptable and remain easy to handle offhand. Oh, and there’s one more thing I failed to mention. The outer tube is finished with black Cerakote, so you get a reduced infrared heat signature. You know, in case you have to take on that alien heat vision eyeballs from the movie Predator. To the naked ear, the overall perceived volume is a little louder than the much larger and heavier .30 caliber suppressors, but for dedicated 300 Blackout use it’s a tradeoff I’ll happily make.

To learn more, visit https://gemtech.com/gmt-300blk.html.

To purchase a Gemtech suppressor on GunsAmerica.com, click this link: https://www.gunsamerica.com/Search.aspx?T=Gemtech.

{ 3 comments… add one }
  • Stephen J Ziegler February 8, 2017, 2:40 pm

    I own two suppressors now and waiting on government processing for the third…about 6 months left! Which is absurd. Congress needs to pass Hearing Protection Legislation ASAP.

  • Michael January 15, 2017, 1:15 pm

    I have and use the SpecWar 7.62 suppressor. I use it on my Remington 700 bolt action rifles in .308, and my AR 15s in 5.56mm and 300 BLK. It works great! If Congress passes the Hearing Protection legislation just submitted, thus eliminating the ridiculous $200 Tax Stamp cost AND the inexcusable 9 month approval wait to receive the suppressor one already purchased all those months ago, I’d purchase more suppressor. However, at my age I don’t have years to sit around and wait for an item that can be purchased right over the counter anytime in most of the free world!

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