There are many good reasons to own a .22LR machine gun. The first reason that most think of, is the reduced cost of ammo. Low recoil, less noise, excellent accuracy and controllability are other good reasons as well.
A 22LR machine gun is likely to be the best gun to use when introducing someone to the Class Three world. 22LR machine gun do not intimidate a novice the way that louder guns with greater recoil do. A 22LR is more likely to create a favorable impression.
The author once took a group of airline flight attendants for an afternoon of shooting at the Triad Action Shooting Klub's range (TASK). Unknown to him, one of the flight attendants was a very anti-gun member of Greenpeace.
Several types of 22LR machine guns were fired. Though the Greenpeace flight attendant had no prior experience with firearms, she became proficient with a 'red dot' sighted, suppressed Ceiner M16/22. At the end of the outing she said, "This is fun. I am going to buy a gun."
Due to their low noise and less demanding needs for a backstop, 22LR machine guns are often welcome in places where centerfire machine guns aren't. Even without a suppressor, a 22LR machine gun is relatively quite. If standard 22LR ammo and a suppressor is used, a 22LR machine gun can be extremely stealthy.
Making a reliable 22LR machine gun is not a simple task. The problem begins with the 22LR cartridge. Being straight and rimmed, it is not well adapted for use in high capacity magazines.
Unless the 22LR high capacity magazine is carefully designed, the cartridges will not feed well. Slightly tapered, rimless 9mm cartridges have had numerous successsful high capacity magazines, 22LRs have had few.
The 22LR cartridge is relatively low powered. It has little excess energy to operate the action. The ability of the 22LR machine guns to operate when dirty varies. Some require frequent cleaning to maintain reliability. Others are more tolerant of fouling.
Warm weather enhances reliability of most 22LR machine guns. The fouling remains soft. In cold weather, it becomes hard and unyielding.
The bolts of semi auto and full auto closed 22s are unlocked when they fire. Only the bolt's mass keeps the breech closed during the high pressure portion of the firing cycle. When firing, the closing bolt strikes the face of the breech and momentarily 'bounces' rearward out of battery.
'Bolt bounce' does not usually cause malfunctions in semi auto closed bolt 22s. Before the semi auto shooter can release the trigger and pull it again, the semi auto's operating spring pushes a 'bouncing bolt' closed. Thus, the problem is avoided.
This is not the case for full auto closed bolt 22s. The full auto's closing bolt releases its hammer (pulls the trigger). The hammer strikes the 'bouncing bolt; before the operating spring can push it back into battery. Unless the 22LR subgun manufacturer has incorporated a way to deal with 'bolt bounce', part of the hammer's energy will be wasted. It must push the bolt closed. The hammer then has insufficient energy remaining to crush the primer.
The usual method of overcomming full auto 'bolt bounce' is to attach a free moving 'anti-bounce' weight to the bolt. During the firing cycle, the 'anti-bounce' weight travels with the bolt but lags behind it. The 'anti-bounce' weight is still moving forward when the bolt strikes the breech. Before the bolt can 'bounce', the 'anto-bounce' weight strikes the bolt and absorbs its rearward momentum. If the designer has correctly calculated the 'anti-bounce' weight's mass and free travel distance, the bolt's 'bounce' will be neutralized.
Open bolt 22LR machine guns are simpler than their closed bolt brothers. 'Bolt bounce' is not a problem for them. An open bolt 22LR machine gun does not release a hammer as it closes. The firing pin of every 22LR open bolt machine gun is permanently set in the bolt's face.
When an open bolt machine gun's bolt is open, it is like a cocked pistol. It is ready to fire. Pulling the trigger releases its bolt. The bolt moves forward and pushes a round out of the magazine. As the round moves forward and upward, its rim slides between the bolt face and the extractor. When the round is fully chambered, it stops moving. The bolt does not. It continues forward a few thousandths of an inch. The fixed firing pin crushes the primer and ignites the powder. Before the bolt can bounce, the cartridge has fired.
The commonest and perhaps best open bolt 22LR machine gun is the American 180. It is the only 22LR machine gun that has been adopted by a government agency.
Firing at 1800+ rounds per minute (rpm), the American 180 sounds more like a chainsaw than a machine gun. The effect of so many small bullets, in such a brief time, is devastating. They will pulverize a cinderblock wall or nibble through a level IIIa vest that would stop a .44 magnum.
The American 180 magazines are extremely high capacity. The smallest contains 177 rounds. The largest holds 275. Firing at thirty rounds per second, even the smallest American 180 magazine will produce thirty-five bursts of five rounds or six seconds of continuous fire.
American 180's rarely need service. If they do however, Val Cooper of E&L Manufacturing can provide parts and expert repairs.