These are factory-new and difficult to find at the moment. These triggers are backordered for many months and in very high demand. With the ATF's current stance on things, who knows if they'll eventually be regulated or the manufacturer will be forced to stop making them. With that said, the Rare Breed FRT-15 trigger is a semi-automatic drop-in trigger that is very easy to install to the AR-15 platform.
It does not make your AR-15 fully automatic or a machine gun under the NFA. However, it does allow the user to fire their AR-15 at a high rate of fire. This is NOT an NFA item, and can be purchased without any special license. In some ways the trigger is like a binary trigger, but it works far better, without question. You can fire single shots, or you can also pull the trigger in a way that allows you to fire your AR-15 at a higher rate of fire.
The manufacturer suggests using a heavier buffer (H3/T3), which helped performance for me. You also need a bolt carrier group that is full auto (like most are today). The trigger is very easy to install and in my experience works incredibly well. The Rare Breed Trigger website does a good job of explaining how the FRT-15 operates, its legality, and also shows you how well it works. You can find their site at www.rarebreedtriggers.com. Please note that the FRT-15 has some issues fitting into Colt AR-15 lowers as well.
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Happy shooting and make sure to buy more ammo for this trigger - you're going to need it!
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