SI-Defense Ambi .308


From Aerospace to Defensive Space, the latest offering from SI Defense brings us a fully ambidextrous battle rifle chambered in .308.

You’ve seen the pictures, and maybe if you’re lucky, even handled one. A fully ambidextrous battle rifle chambered in .308 that weighs in at 8.5lbs? Yes, and it shoots like a dream as well. I am talking about the Si-Defense SI-D Ambi .308. Based out of Kalispell, MT, SI-Defense is poised to take the AR-10 market by storm with this new concept rifle that will hit the market soon.

Unlike many other AR companies on the market; SI-Defense offers true ambidextrous controls; with a mirrored bolt catch and mag release button on either side of the rifle, unlike some companies with bolt-release only levers on the right face, or an internal workaround system utilizing the mag release button for multiple purposes.

SI-D Features

  • Ambi SI-D 308 7075 Billet Lower Hard BLK Anodized
  • Ambi SI-D 308 7075 Billet Upper Hard BLK Anodized
  • Ambidextrous Mirrored Controls-Billet Machined Bolt/Mag Release
  • Ambidextrous Take Down Pins
  • Quick Snap Dust Cover
  • Forward Assist
  • Flared Magwell
  • Integrated Trigger Guard
  • Barrel: Military Approved PROOF Research Carbon Fiber Wrapped 16” 1:11.2 Twist
  • Light Weight Free-Float 15.5” Key-mod
  • CMC Trigger
  • Mission First Tactical Stock
  • Charging Handle: Ambi
  • Battle Arms Development Selector
  • Muzzle Break: Fortis Red
  • 20 Round Mag Included

The upper and lower receivers of the SI-D Ambi .308 are fabricated out of 7075 Billet aluminum and hard anodized in-house.

Interview with Jason Sonju

So, who are SI-Defense, and why are they worth a look? I had a chance to talk with Jason Sonju, who gave me some insight into who SI-Defense is, and why they are not to be taken lightly.

CT: How did SI-Defense come to be?

JS: SI Defense is a spin-off of Sonju Industrial (SI). Sonju Industrial is an aerospace manufacturing company that builds components (missile, fighter, torpedo, commercial aircraft, ect.) for major primes like Boeing, Lockheed Martin, Raytheon and United Technologies. Sonju Industrial started manufacturing gun parts in 2006, primarily .223/.308 receiver sets, and handguards. The business of building gun parts became big enough to start a separate company which I named SI Defense. To come up with the name, I took the “S” and the “I” from Sonju Industrial and added “Defense” thus, SI Defense (SI-D) was born. SI Defense has been building parts for nearly a decade…recently Melinda (Author note: Jason’s wife) and I decided to re-brand the business and build complete rifles. The last two years we have been developing technology, filing for patents, and re-organizing SI Defense.

CT: What are the overarching business philosophies that drive your company, and what edge do you offer the industry that sets SI-Defense apart from the rest of the industry?

JS: SI Defense (SI-D) uses the same aerospace philosophies and methodologies that Sonju Industrial does. We are basically taking aerospace manufacturing and infusing it into our firearm manufacturing. SI Defense is a true firearm manufacture because it can design, engineer, manufacture, process finish (Anodizing), assemble and test its firearms. That is why we are so dangerous in the industry.

We have the ability to proto-type rapidly, and take an idea to market quickly. We are relatively “unknown” now, but I believe with strategic marketing, and quality products our name will grow. We plan on hitting the road hard in 2015, and it will be interesting to see what position we are sitting at this time next year.

I also believe we bring another element to the table and that is we are real people. Melinda and I are hunters, shooters, and outdoor people who bring realism and normalcy. As owners, we want to be accessible to the consumer by interacting and listening to their stories. We also have a deep respect for military and LE…both of our fathers served our country and the fact that we build parts for our military brings a deep satisfaction that we are contributing some way somehow to our country. It shows in how we run our business, and how we build our firearms. We also believe that we have an obligation to build God’s kingdom no matter what it is… for now its building firearms down the road, who knows?

CT: Without giving away any proprietary information, can you explain your design philosophy and process?

JS: Innovation. Our mission statement is built around innovation without jeopardizing reliability. “Success without Compromise”. The AR world is flooded right now and everybody is jumping on the band wagon. So what’s different about SI Defense?

We want to be known as an innovator, a company that is always improving and releasing new and better products. We have a ton of veterans that work for us, including resources in the aerospace community that we lean on for ideas and improvements. We also look for feedback from the shooters, and hunters. After gathering this information, Melinda and I sit down with our engineers and lay down the vision of what we are looking for.

Being a design, engineering and manufacturing company we have the luxury of building pretty much anything…but the industry can only handle so much change whether it’s a “look” or a new “technology” so we have taken the necessary steps to introduce new stuff slowly. As we get known, we will begin to introduce some radically different stuff. I truly believe, with proper marketing we can be a major player in this industry. We are partnering with strategic OEM’s and I think this is key. We are partnering with those who share the same philosophy and passion and are willing to take calculated risks. With God’s grace and mercy I think the sky is the limit.

CT: I’ve had the opportunity to handle and fire the 556ATC and the SID Ambi .308, both are very impressive. What does the future hold for SI-Defense, and what other platforms can we expect to see in the future?

JS: We have always built a standard no frills AR rifle. Personally this has always bothered me because it’s so boring and plain and looking back, it’s actually hurt our company. But in reality, you have to offer it because people expect it. Melinda and I wanted to offer an AR-rifle that could compete with anything on the market, thus The SI-D .308 Ambi Battle Rifle was born.

Personally, I think this rifle can compete with anybody’s rifle. With the carbon fiber barrel I believe it’s in the top three. We are currently working on the AR-15 Ambi Battle Rifle and it should be out second quarter 2015. We also have a modular monolithic .308 Ambi quick-change barrel system coming out in the summer of 2015.

We also have the Petra AR .300WM coming out at the shot show for the public to see. Testing is going great, and I believe this will spawn some excitement. It is truly bad-ass. We have another platform called the “Exodus” which is a .300-.338 AR Rifle that is truly ambidextrous and can ejected the round on the left or right side. What’s unique about this platform is that it can shoot any round between the .300 and .338 by simply changing out the bolt and barrel. You can keep all the other components intact which basically alludes to having two different calibers using one weapon platform.

We have another platform called the “Megiddo” which is a blow-back roller system AR. We have built proto-types and testing shows promise. I’m very excited about this platform.

Finally, we have plans for bolt-action rifles… not just any bolt action, but innovative technology driven.

The barrels that Jason alluded to in the Q&A are the new Proof Research carbon fiber-wrapped barrels that will soon be shipping with the complete rifles. The T&E SI-Defense .308 that I had an opportunity to shoot recently did not have this barrel installed, but I eagerly look forward to getting a retroffited model to run in the near future.

From the bench, using a 1-4X24 vortex scope and off-the-shelf PMC 147 grain .308, my shooting partner was able to get 3 of his 5 round group touching at 100 yards and all within a 1.5” grouping. I am not that strong of a long distance shooter myself, so I could not replicate that, but was able to stay within 3”, which for me is pretty good. The rifle definitely shoots better than I do.

Off of the square range, I had a brief chance to shoot the SI-Defense both left-handed and right-handed. As a natural southpaw, I was of course interested to see how the ambi controls worked, and they came through flawlessly. I’m sure the right-handed shooters will be happy to have the chance to run an AR-platform rifle with the fully ambidextrous controls, as locking the bolt back as a right-hander can now be more easily achieved without add-on hardware.

All in all, I think this is a very promising rifle; chambered in .308, fully ambidextrous, and weighing no more than my venerable patrol rifle in 5.56, resulting in a comfortable, easy-to-shoulder rifle that packs quite a punch.

Keep an eye out on SI-Defense, I believe they have a lot to offer in addition to their formidable first shots into the AR platform market.

For more information, check SI-Defense out at:

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