Testing Sig’s .300 Blackout Short Barrel Loads

Sig Sauer 300 BLK

The Sig Sauer BLK SbR Elite Copper Duty Ammo brings 120-grains to the table. (Photo: Josh Wayner)

Sig Sauer recently released a new 300 Blackout ammo offering for shooters looking to elevate their short barrel game. The 300 BLK SBR Elite Copper Duty Ammo aims to bring more capabilities to AR shooters, delivering a new round designed specifically for short-barrel firearms. As something of an ammo guy, I wanted to bring the Guns.com readers an in-depth look at the brand-new Sig Sauer 300 Blackout 120-grain Short Barrel load.

Unpacking the Sig 300 Blackout

While the box is relatively unassuming, what lies within is anything but. The load is visually appealing and features a long, slender copper projectile, blackened brass, and a silver primer. The cartridges resemble classic Russian military ammo. Unlike the old Soviet ammo, the Sig load is not lacquer coated.

Russian ammo cases were traditionally made of steel and had a thin coating on them to allow for extraction and to reduce wear on the gun. Sig’s opts for a brass case with a dark, non-reflective wash. This quality is both attractive and distinct from other 300 Blackout ammunition.

Surprisingly, most makers do not build 300 BLK ammo for short barrels despite the fact that most people consider the cartridge to be dedicated to short pipes. This is the same problem that exists with cartridges like .38 Special. Ultimately, this means ballistics on the box aren’t always what you get when you fire.

Sig Sauer 300 BLK

The ammo performed well during testing, holding up against a variety of targets. (Photo: Josh Wayner)

Understanding the 300 BLK requires forgetting everything you know about rifle rounds. The round is in a class of its own and is more akin to 30 Carbine and .45 ACP than it is 5.56mm, 308 Win or 6.5 Grendel, but it plays in the same fields as the latter rifle rounds. The round reaches peak pressure and velocity in only a few inches of travel in the barrel due to the fast-burning magnum pistol powder it uses. This allows it to be chambered and used in barrels as short as 5-inches but also in barrels three times as long or longer. The execution of the Sig 120-grain Short Barrel load is extraordinary as it managed to tackle three difficult things perfectly — accuracy, velocity and bullet performance.

Testing the 300 Blackout

Just for fun to test these loads out, I loaded them into Magpul PMAGs dyed to look like the famous AK-74 bakelite mags so common in 1980’s action films. The gun used to test the Sig ammo sported a Faxon Firearms 7.5-inch barrel. This barrel is well-used despite being two years old and has seen roughly 10,000 rounds. I trust this barrel to deliver accuracy as it has shown very little, if any, change in group size for control ammunition over time. A control load is handy as it gauges barrel performance over the life of the barrel. Control ammo for this review is handload featuring a 125-grain bullet and prepared to match-grade standards.

The load averaged 2.5-inches at 100-yards for 50 rounds and ten groups, which to many isn’t impressive, but to me, it is pure gold. The 300 BLK is essentially a pistol round that masquerades as a rifle round and behaves as such. The cartridge uses pistol powder and pistol ammo tolerances as far as accuracy is concerned. Extraction and ejection were healthy with no Signs of overpressure or primer separation.

The velocity of this round was calculated via an Oehler 35P chronograph. Sig’s box states a predicted velocity of 1,897 feet-per-second from a 6.75-inch barrel. The 7.5-inch barrel I used generated a bit more at 2,010 fps. The combination of the barrel used for this review and the adjustable bleed-off gas block from Superlative Arms on the gun produced a faster velocity. The standard deviation on this load was 51 fps for 20 rounds — fantastic for 300 BLK.

Sig Sauer 300 BLK

In bare gel, the lead free monolithic copper bullets expanded reliably. (Photo: Josh Wayner)

When it came to bullet performance, Sig did this one just right. I tested the load against barriers, bone, and in gel. The lead-free monolithic copper bullets performed with great repeatability in the mediums I tested it in. In bare gel, the bullets expanded reliably and passed fully through the 16-inch block from Clear Ballistics. Recovered projectiles maintained 99-percent of their weight, but it’s fair to say that they didn’t lose mass at all.

In bone and hard mediums, the bullets tended to pass through without expansion and then open up in the hiding behind. The recovered bullets were almost indistinguishable from the ones fired into bare gel and did not show Signs of material loss. Passing through bone yielded the occasional bullet that exited the gel completely, simply plopping out on the other side having lost most their energy.

Fianl Thoughts

The results I obtained with this ammunition were nothing short of exceptional. I have a great deal of experience with Sig Sauer ammunition and was pleased that they delivered here where so many others have failed. Out of the 25,000 or more rounds I have fired in the last several years, through a great many physical objects and barriers, I can honestly say that I was impressed with what Sig did here. Do yourself a favor and check out the 120-grain 300 BLK Short Barrel load for yourself. You’ll be glad you did.

The Sig Sauer 300 BLK SBR Elite Copper Duty Ammo retails for $29.95 for a box of 20.

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