Building My Own .300 Blackout Rifle: Guide & Testing

Last Updated on April 4, 2024

By Trampas Swanson

The world of hunting is an ever-changing environment from the hunters’ strategies to the tools in which are used to make harvesting their game successful. For years, lever action and bolt action rifles ruled supreme in the medium sized game category, and they mostly used variations of the .30 caliber platform. From the classic 30-30 to the favorite .308 and 30-06, endless volumes of data have been gathered, researched and practically perfected. As each new generation passes and a new flock of hunters enter the scene, the market sees a new evolution of products and techniques.

The turning of a new millennium saw a large growth in hunting culture with new hunters from all walks of life coming into the sport. With the AR-15 platform consistently outselling every other rifle on the market, manufacturers wanted to expand its use for hunting beyond the varmint category into the wider spectrum of the medium game genre. While many sought to fill this void, it was the .300 Whisper designed for the SPEC OPS community that blazed the way for Remington and the Advanced Armament Company to achieve commercial success with the .300 Blackout or BLK round.

Based around the concept of seating the historically popular .30 cal or 7.62x35mm bullet into the ever popular 5.56x45mm casing, performance could be dictated by the grain weight of the projectile from super sonic to subsonic for those who run suppressors on their rifles. With a full burn length of only 8 inches of barrel, this would be the perfect set up for a Short-Barreled Rifle or SBR project designed to be a close action brush gun. This would be the perfect set up needed for the thick swamp areas of north Florida where our team of writers and I generally hunt white tail deer and hogs.

Building the .300 BLK Project

Early last year, I decided to start a personal build project based around the .300 BLK cartridge for mostly hunting applications within 50 – 150 yards. I started the project with a custom built 9” barrel with a 1 in 8 twist for the most versatility in ammo selection. My short-term goal was to learn the performance characteristics of the .300 Blackout platform using a variety of bullet weights. Once this was accomplished, I would eventually run the rifle as a dedicated suppressed firearm for hunting as the long-term goal. After a period of ten months, the first tax stamp for the construction of the SBR was received. Using a combination of a Spike’s Tactical upper, lower and rail with Magpul stock, pistol grip and as well as their new .300 BLK dedicated Magpul PMAGs, I was almost ready to hit the range to get started.

Two items needed to wrap up the build and be vital to performance at max intended distance were a quality trigger and dependable scope. For the trigger, I went with one of the most respected names in the industry, Timney Triggers. Their drop-in 3lb triggers have always proven to be crisp and light enough for breaking precise long-range shots while still heavy enough to allow my finger to apply pressure as I begin my shot process. The singe unit construction was so easy to install, my 3-year-old could have done it.

To top off the project, the great folks at Vortex Optics sent over their new Strike Eagle 1-8×24 scope. These handy scopes are quick to get on target and durable enough to survive the thick underbrush of the north Florida landscape. Combining the Strike Eagle with one of my favorite one-piece AR mounts from American Defense made for a rock-solid scope / mount combination to get started!

Range Time

To function test and zero my scope, I headed to our private testing grounds affectionately referred to as the “The Swamp” to meet my good friend and local hunting guide, Kevin Fulford. Aside from just being able to enjoy a day shooting with a buddy, there were two additional benefits of having Kevin along. Kevin already had firsthand knowledge of hunting with the .300 BLK in the AR-15 platform as well as doing so regularly with his AAC suppressor. Knowing the long-term goal of my SBR project to be a dedicated suppressed rifle, Kevin brought along his suppressor to use in helping me gain data on the new build.

To develop a base line for testing, I brought along an assortment of supersonic and subsonic loads from trusted manufacturers in the industry. Included in this assortment were a couple of boxes of 150 grain full metal jacket ammunition from our good friends at Fancy Brass Co. If you haven’t heard of this small company, they have developed a solid reputation and great personal track record in our previous reviews. In addition to this ammo would be Remington’s 220 OT FB (Open Tip, Flat Based), Hornady’s Custom 110 grain V-Max and Hornady’s Black 208 grain A-Max rounds. Shooting from the bench position, Kevin and I chose to start at 50 yards and work our way out to 150 yards as things progressed.

In breaking the first shot using the Fancy Brass Co. ammo, the trigger was just as comfortable and crisp as many of my small-bore target rifles. Following up with two additional shots, I ended up with a 1-hole group approximately 3 inches right of center and 1.5 inches high. With a few quick scope adjustments, I fired two more three shot groups. One more small scope adjustment for windage and the rifle was exactly where I needed, holding center about an inch under the bullseye. The second group had two holes touching and the third about 1/8” to the right. The third group resulted in the same 1-hole group as the first.

Satisfied with the results for the time being, I decided to move out to 100 yard mark to see where my hits would score on target. My first three shots at the new distance were ¼” to the right and slightly high. This group had two holes touching and one slightly to the right. With just two adjustments, the scope was zeroed at 100 yards with the next three shots touching each other in the center of the bullseye. My confidence in having put together a solid performing rifle build was beginning to feel validated at this point.

Finally, I moved out to 150 yards, which is typically the furthest available shot in the given hunting area we roam. With the next 3 shots, the group was still tight but moved roughly 4 inches down. Having the bulk of my high power rifle experience being with calibers such as .223, .308, .270 and .260, seeing a drop such as the .300 BLK at this relatively short distance was a new experience for me. Without adjusting my scope, I decided to confirm the first grouping. Both the second and third series of shots resulted in overlapping groupings. Now with a firm baseline backed up with similar data from Kevin shooting the same series at the same distances, it was only a matter of gathering more information at set distances with other loads before comparing to the same data once suppressed.

Moving on to the 110 gr V-Max loads from Hornady, each group was solid and consistently 1 – 1.5 inches high from the zero set with the 150 grain Fancy Brass loads. The accuracy was solid at each distance but did not seem to be as consistent as the baseline loads in their groups. Switching to the much heavier Remington 220 grain loads, the groups “submarined” every mark set by the baseline data. At 50 yards, the groups were roughly 3 inches lower than the lighter loads and holding around 1 inch to 1.5 inches at 100 yards, 2 inches consistently at 150 yards and a full 5 inches low.

Finally, Kevin and I came to the Hornady Black 208 grain A-Max loads. The recoil seemed to be a slightly smoother feeling impulse into the shoulder when shooting. This allowed for a better chance to track the round’s bullet trace through the scope when zoomed up to 8x power. While still a bit lower than the baseline zero, groups were tight and did not seem to drop as fast as the Remington loads. There was roughly only a 1 inch or less difference between it and the baseline drops at each distance. The rifle noticeably seemed to like this ammo the best while running unsuppressed.

Going Suppressed

With ample amount of time on the bench making notes with each shot group, it was time to start logging a bit of data using the AAC 7.62-SD suppressor from Advanced Armament Company. Again, starting with the Fancy Brass Company loads, I was eager to see if there would be an impact shift. I shot three rounds at 100 yards and confirmed my groups were only a ½ inch diagonally to the right of dead center. Kevin’s three follow up shots landed between center and the outside shot of my group. The sound was noticeably quieter but still accompanied by the loud crack of the supersonic ammo. At the 150 yard mark, the group was an only ¾ inch from the confirmed zero I had noted for that distance. Changing over to the Hornady Custom 110 grain loads, the data was very close at both distances. Again the supersonic rounds were quieter but not as much as the 150 grain loads. I was impressed that despite the 30 grain difference, the Fancy Brass Co. full metal jacket ammo delivered practically the same performance as the Hornady V-Max load. If I trained with the cheaper Fancy Brass load and hunted with the Hornady V-Max, it would be a good trade off in cost and effectiveness.

The high and low of this test session started with the Remington 220 loads. The recoil seemed to thump a bit more and resulted in a 6 inch drop at 150 yards. Groups went from 2 inches at 100 yards to erratic 2.5 – 3 inch groups at 150 yards. Although this was the quietest load shot all day, it also offered the most disappointing results. In switching over to the Hornady Black 208 grain loads, it was time for the rifle / suppressor combo to shine.

Posting up less than 1 inch groups at 100 yards consistently between Kevin and I, the shift was minimal to under an inch. Moving to 150 yards, I was able to hold shot groups under 1.5 inches despite the point of impact drop from the lighter and faster 150 grain Fancy Brass Co. zero as expected. By the end of the day, the winner out of the sample loads tested was clearly the Hornady Black.

Advanced Armament Company – AAC 7.62-SD suppressor

• Attachment: AAC 51T quick disconnect Breakout flash hider.
• Sound reduction: 30 dB
• Weight: 23 ounces
• Length: 9”
• Build materials: stainless steel; Inconel
• Finish: high-temp Cerakote
• MSRP: $519 – $699

While testing different loads for my .300 BLK project, I was able to get some significant data on how the rifle performs with and without the suppressor to work with moving forward. Since our range time working with the AAC suppressor, I had the pleasure to meet the great folks at Torrent Suppressors while at SHOT SHOW in Las Vegas. Once I got to know everyone with the Texas based company, I took them up on an offer to be on the Torrent Suppressor test team.

With the end goal of running the .300 BLK project as a dedicated suppressed rifle, I acquired one of Torrent’s model T-3 .30 caliber suppressors. This direct threat suppressor looked good and seemed to balance the rifle out well once mounted. Due to the lengthy time limit of the paperwork to clear the ATF, I was limited to initially testing the suppressor on a dimly lit 20 yard indoor range at the shop.

Immediate testing proved to be very impressive but not a true measure of what the Torrent Suppressor was capable of until we are able to test in the field. After running the same brands of ammo through the T-3, the day ended with solid results regardless. Two important notes were the lack of shift in zero between the suppressor being on and off the rifle, and the Hornady Black 208 grain round performing at the top of the list. Not to take anything away from the AAC suppressor we originally tested, the T-3’s amazingly quiet performance given it’s more compact size is a great step moving forward.

Torrent Suppressor T-3

• Caliber Rating: .30 CAL/ 300BLK/ .308/7.62NATO / 300 Win Mag
• Thread Pitch: 5/8 x 24
• Color: Black / FDE
• Color Finish: High Temperature Cerakote
• Length: 7.75”
• Diameter: 1.48”
• Weight: 16.5 oz
• Sound Reduction: 25 to 39 dB
• Material: 17-4 Stainless Steel
• MSRP: $650

Final Thoughts

Overall, my experience with the .300 BLK cartridge and the project rifle was hugely positive. The 1-8×24 Strike Eagle scope from Vortex was a very impressive little optic. The short, compact design did not seem to add much weight to the rifle and offered very quick target acquisition while shooting freehand, even when the zoom was dialed up to 8x power. Given the generous eye relief of the Strike Eagle, I may have to consider buying a second one for my scout rifle set up in .223. As I continue to gain data and experience with the new rifle and loads in relation to zero and hold over, I can’t wait to hit the woods hog hunting this summer and whitetail deer in the fall.

If you are looking to get into hunting, the .300 BLK is offered in many great packages such as the Remington 700 bolt action and almost every AR-15 manufacturer. There is a new generation of hunters coming into the sport every day and the AR-15 is slowly making a strong presence in the hunting world despite efforts to demonize the rifle. It is up to all of us as shooters, collectors and hunters to stand our ground and support those who help fight for our gun rights. As for myself, being a LIFE MEMBER of the NRA as well as an AR-15 armorer, it is very satisfying anytime I put together a rifle to enjoy successfully in the field hunting and enjoying our Second Amendment freedoms. If you own an AR-15 in .223 / 5.56, this is definitely the next step of progression in enjoying all the benefits the platform offers. Additionally, I highly recommend running one suppressed! Until next time, if you want to know more about a product, make sure its Swamp Tested, Swamp Reviewed!