I have a single AZR-15A1 Forced-Reset Trigger assembly for AR15 platform rifles. This is about as close to 'full-auto' as you're going to get.

AZR-15A1 ARIZONA REGULATOR + COMBAT TRIGGER  / Complete ARIZONA REGULATOR System AZR unit AZR FCG and Std Mil-Spec 3 Position Selector

100% Drop In System using provided Std Mil-Spec Hammer and Trigger Pins

Use the Provided 3-Position Mil-Spec Selector

OTHER TRIGGERS ARE NOT COMPATIBLE WITH THIS AZR-15A1 COMBAT TRIGGER SYSTEM.

These are extremely hard to come by and sell out within a minute of drop. I've had to write a script and create a bot, just to get one purchased, due to the high-demand and difficulty of being able to add to cart and check out before sold out. Furthermore, they only allow 1 max unit per customer. 

Was going to drop this into another build but have decided to go another route. 

$450 Firm

Pick-up in Belton, TX

TRIGGER TEST - https://www.youtube.com/watch?v=W4E1Eze3VpY