I don't like drop-in auto-sears! Not because they don't work, because they do. They not only work, but in my experience an AR-15 equipped with a drop-in auto-sear works as well as an original government issue M-16.
The problem's not with the auto-sear, it's with the laws governing its use.
The drop-in auto-sear was designed in the mid 1970's for the sole purpose of converting the AR-15 to fire full-autD (select fire].
If you buy a drop-in auto-sear that was manufactured after November 1st, 1981. it is by itself classified a machinegun, and must be serial numbered and registered with B.A.T.F. as such. If it was manufactured before then, it in itself is not a machinegun. Of course, if you put it in your AR-15 then it is a machinegun. and as such is illegal, because although it was manufactured before, but not registered before midnight May 19. 19B6 it can not be registered after that date.
If you have all of the above listed parts BUT NO GUN, under federal law you have a machinegun. That may sound crazy, but that's the law.
The fact that a post November 1st. 1981 drop-in auto-sear must be registered as a machinegun is bad news. If you bust it. to get your gun working again you must not only buy a new one for anywhere from two to three hundred dollars, you must also pay the $200.00 tax on the new one.
If that's not bad enough, if you shpuiil lose it. you have lost a machinegun and B.A.T.F. gets very unhappy about that.
One last thing about using the drop-in auto-sear. With the sear removed from the weapon, you would think you once more have a legal semi-auto firearm. NOT SO! With the necessary M-16 parts installed, if you put the selector on full-auto the disconnector will not work. The hammer will follow the bolt forward if you hold the trigger back. This causes what is knows as slap fire and is dangerous. If the bolt has not locked before the cartridge fires you will have one hell of a blast coming out the ejection port. That's bad, but worse is yet to come. B.A.T.F. has ruled, if a weapon will fire more than one shot with each pull of the trigger, it's a machinegun.
Even though you believe you did everything right and paid the tax on the drop-in auto-sear, by putting the other M-16 parts in your AR-15, you have unwittingly manufactured an unregistered machinegun.
You would at that time be liable for a fine and imprisonment.
TO RECAP: to buy a registered post November 1st, 1901, drop-in auto-sear from a Class III dealer is legal.
To have an AR-15 with M-18 parts installed is illegal
To have M-16 parts although you have no gun is illegal.
To have an unregistered drop-in auto-sear is illegal.
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