Stag Arms uses the designation of STAG-15 and STAG-16 as rifle designations instead of AR-15 and M-16 due to them being trademarks of another manufacturer.

Side by side, the STAG-15 and the STAG-16 look quite similar, to the point that many affirm they are the same rifle with a different name.  

Nothing can be further from the truth, starting with the fact that the STAG-15, which is targeted mainly at civilian users, is a semi-automatic rifle, while the STAG-16, which is used by police and military, is a select fire rifle which can shoot in a semi-automatic mode, burst mode, or in a fully automatic mode.

STAG-16’s and all other select fire, burst fire, and fully automatic firearms have been strictly regulated since 1934 and no new firearms of these types have been permitted for sale to private owners since 1986. Possession of any select fire, burst, or fully automatic parts except for the bolt carrier are illegal unless the firearm is already privately owned and registered with the NFA branch of the ATF.

It’s All In The Small Parts

Since the STAG-15 and STAG-16 look very similar there are a few ways to tell them apart:

Trigger

Take a good look at it from the top. If it has an open channel which goes all the way through the back end, you are holding a STAG-16 trigger. If the back end is closed, it belongs to the STAG-15. This channel is used to fit the disconnector.

Disconnector 

The STAG-16 version has a “tail” at the end of it compared to the STAG-15 disconnector. This tail interfaces with the auto sear during burst or full auto operation.

Hammer

Like the disconnectors, STAG-16 hammers also have extra metal called a “hook” on them which engage the auto sear.

Auto Sear

Only found in STAG-16 rifles, the sear interacts with the hammer, disconnector, and bolt carrier to allow burst or fully automatic shooting.

Bolt Carrier

A STAG-16 bolt carrier will have more metal on the bottom at the back of the carrier than a STAG-15 bolt carrier. This is the only STAG-16 part allowed in the STAG-15.

Safety Selector 

The STAG-16 safety selector is designed for safe, semi-automatic, and burst/fully automatic positions on the lower receiver, it also has more cutouts on the inside than the semi-automatic. The STAG-15 safety selector only has one cutout which is for semi-automatic shooting and has two positions.

Lower Receiver

The lower receivers for STAG-16 rifles have two additions to them when compared to the STAG-15 lower receivers. The STAG-16 receivers have “Auto” or “Burst” engraved around the safety selector area and an extra hole for the auto sear pin. The shelf on the inside of the receiver is machined down so there is room for the auto sear.

Key Takeaway:

In the end, STAG-16 rifles have many different parts compared to the STAG-15 and these parts are not easily changeable, and precise machining of the receiver is required. Manufacturers won’t sell any burst fire or fully automatic parts except for the bolt carrier except to people who can prove they already have a STAG-16 rifle.

Newly manufactured STAG-16’s can’t be purchased except by government entities such as police departments. Personally owned legally transferred STAG-16’s usually sell for $12,000 to $20,000 and need to be transferred through the ATF’s NFA branch and a special “class 3” firearms dealer.

Image Courtesy of: "Stag Arms Model 3G" & BigOnline.org