What separates SI Defense from the pack in the highly competitive industry of AR rifles is that the company designs, manufactures and assembles all of its own products in house. 

SI Defense is a division of Sonju Industrial, which started out as a small autobody shop in Kalispell in 1978. Owner Richard Sonju added powder coating and anodizing processes to his shop’s services and it soon began attracting business from such aerospace giants as Boeing, Lockheed Martin and Raytheon. 

By degrees, Richard and his son Jason built Sonju Industrial into a leading aerospace manufacturing plant. In 2008, SI Defense was started, adding custom firearms to the company’s aerospace manufacturing capabilities, a natural evolution for a state-of-the-art machine shop that already was utilizing horizontal machining centers to precision-cut metal and cellular technology. The company also uses 7075 aluminum solid block billets in the manufacturing of its upper and lower receivers. 

“It takes four times as long to make a rifle from a billet compared with forging the metal and the deburring process also takes longer,” SI Defense Manager Chris Baldwin said, “But the result is a better built, more durable custom-fit rifle.”

SI Defense has lead the market in utilizing titanium in an AR platform, Baldwin said, adding that titanium is one of the toughest, lightest metals in existence and known for its corrosion resistance — but it’s also difficult and expensive to machine.

“We’re ahead because of the investment in our machinery and we’re second to none,” Baldwin said. “SI Defense focuses on quality over mass production. We have a highly skilled work force of aerospace machinists making our firearms.”

 A Montana native and Vietnam veteran who was wounded in the war, Richard Sonju employs a good number of veterans in his 50-plus work force.

The company’s arsenal of AR rifles caters to military and law enforcement, as well as sportsmen.

“We’ve become more popular to the sporting world because of our rifles’ versatility,” Baldwin said. “You can easily change calibers and configurations, barrel length, the furniture and the optics. There are all kinds of gadgets that fit our AR guns.

“Firearms manufacturing is one of the most positive, growing businesses in the country,” he said, “and it’s a particularly positive force in the economics of the Flathead Valley.

“It all comes down to the fact that Montana is friendly to the Second Amendment,” Baldwin said. “The industry recognizes that Montana has less legislation on the manufacturing of firearms and so the industry can produce a good product without the burden of heavy restrictions by the state.”

For more information, visit www.si-defense.com or call 752-4253.

Reporter Carol Marino may be reached at 758-4440 or by email at community@dailyinterlake.com.