The Legalities of Class III Firearms

Another misconception perpetuated by Hollywood and the media is that it is easy to convert a civilian AR-15 into a select fire weapon. It is not easy. Back in the good old days I built a select fire gun from an all Colt AR-15. It was quite a bit of work to make the conversion and not something just anyone can do in the garage with a hammer and a pipe wrench. It also required some intricate machining to make the parts fit.

The M-16 was a break through in the Vietnam war but had problems at first.
The M-16 was a break through in the Vietnam war but had problems at first. It has been our battle weapon for over 30 years.

I wish I still had that gun. Access to M-16 internals is also limited these days. They are available for repairs of existing guns and to law enforcement and military armors. Any yahoo who tells you that you can buy machine parts at the local gun show is an idiot.

There are some malfunctions that could turn an AR-15 into a “machine gun,” but only in respects to the letter of how the law is written. The definition of a machine gun is one that fires more than once with one continuous pull of the trigger. If the disconnector and trigger group are not properly fitted the gun will fire when the trigger is depressed and the disconnector will not hold the hammer for the sear and it will fire when the trigger is released. Two shots for one pull of the trigger. This can also happen when replacing AR parts with M-16 parts incorrectly.

This is by law a machine gun but not near as much fun as a real one. If your AR has this malfunction you need to have it repaired immediately because you can still be prosecuted for possessing a machine gun. To me this would be like getting a DUI on one beer.

I recently saw a CSI show where they inferred that a drop-in auto sear was all that was necessary to turn an AR into a machine gun. If only it were so simple. A drop-in auto sear is just that, drop-in. Factory M-16s have an auto sear that is held in place with a pin that goes through the frame like the other pins that hold in the trigger group. The drop-in fits differently.

The legal AR-15 will still need an M-16 trigger group, a bolt carrier and selector switch to operate. Most likely there would have to be some machining of the receiver also. So what they are saying is only half true. It’s much like CSI’s investigating homicides, arresting offenders, and doing dynamic entries.

Oh that’s right, that isn’t even a half-truth because I am retired from one of those departments that CSI is based on. Problem is voters believe what they see on TV.

AR-15 parts differ from M-16 parts. Some of the differences are subtle like the trigger and disconnector. The bolt carriers have big differences in that the M-16 carrier has more metal further back on the bottom groove. This metal contacts the auto sear when engaged causing a bypass of the trigger sear engagement.

The hammer automatically falls when the bolt closes causing another round to discharge. The safety/selector switch on an M-16 has many more grooves and bumps than an AR switch. These allow proper sear engagement for full-auto fire. The guns are also easily distinguished from common AR-15s by the existence of an auto sear and pin, the differences in the parts, and factory machine guns have auto stamped next to the selector switch. All of the parts have to be installed and tuned for it to work properly.

If you decide that you want to get into this type of weapon you will have to weigh out the costs and fun of owning one. For most defensive purposes, police work, and even many military missions, the full-auto aspect is used very little. Unless you have the need to clear some jungle, heavy brush, or lay down enemy sniper suppression fire, it is an expensive way of having fun. A three-shot burst feature would be like an automatic double (or triple) tap and far more useful for defensive purposes.

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