The Sig Sauer 556 Classic SWAT rifle was Sig Sauers attempt at bringing an updated version of the Sig 550 series of rifles to the North American shooting market. Like the Sig 550, the Sig Sauer 556 never gained traction, It wasn’t a mistake on Sig’s part so much it just was a rifle that was lost in a sea of cheaper rifles. The AR-15 had been for the most part standardized long ago and was considerably cheaper than the Sig Sauer 556. In the whirlwind of the anti gun movement at the time the rifle was released its easy to tell why consumers chose to spend their money in rifles they knew like the AR-15 rather than new rifles they might not have known much about like the Sig Sauers 556 Classic SWAT. I have been intrigued by the Sig family of rifles for years so when I had a chance to acquire a Sig Sauers 556 Classic SWAT that had a very low round count, I had to grab the opportunity and take a risk.

If i had to describe the Sig 556 Classic SWAT I would say its the best parts of the AR-15 mated with the AK-47 with a dash of Swiss style and quality control added to it. The rifle takes the standard AR-15 magazine and fires the 5.56 x45 cartridge but essentially uses an AK-47 type of gas system that is adjustable. It’s an appealing idea for sure, something that uses magazines that most gun owners that read this site have, firing a round that is available just about everywhere, but isn’t the standard boring old AR-15 that we all own. We figured that since some of our readers may not know about the Sig 556 family of rifles we would make a list of what about the Sig 556 is similar to the AR-15 we all know and love, and what is different about it.

What’s Similar to the AR-15 ?

  • Barrel length
  • Uses standard AR-15 magazines
  • Magazine release and location in same spot at as AR-15
  • 5.56 NATO chambering
  • 1:7 twist rate

What’s Different ?

  • Different trigger
  • Stamped Steel vs Aluminum upper receiver
  • Different bolt
  • Different recoil system
  • bolt release operates slightly differently
Authors Photo

Breakdown and Operation

Now that I have the luxury of owning a Sig 556 rifle I am amazed at how easy it is to become familiar with, being a current AR-15 and AK47 owner its a very natural transition to the Sig 556. The receiver breaks down like an AR-15 using two push pins to separate the upper and lower halves of the gun, the bolt however is a bit different. The rifle lacks an AR-15 style charging handle, instead it has one on the bolt similar to the AK-47, but with a twist. The bolt handle is removable to allow the bolt to slide out the rear of the rifle, again like the AR-15. Like I said in the beginning this rifle is a hybrid of both designs.

Once the bolt slid out of the upper receiver it was like I was looking at a slightly modified AK-47 bolt carrier group. In the image below you can clearly see the pronounced angled ramp on the rear of the bolt and the rotating head and locking lugs on the bolt itself. When you hold the two bolt side by side it becomes obvious. One of the major differences between the two bolts though is that the AK-47 pattern bolt is set up to accept a recoil spring from the rear and the Sig 556 bolt uses a piston system and the recoil assembly meets the carrier just above the bolt. The lever shown n the Sig bolt is what you depress to remove the charging handle.

Authors Photo

Different Style of  Trigger