I hope Marco's wrong about that, but I wouldn't be surprised if he's right, and I agree completely with his advice: leave that thing out of the rifle, and replace the trigger group for good measure; I would also want to be sure a gunsmith checks things over carefully to make sure there are no other surprises.
The replacement trigger group shouldn't be too expensive, and the original should still have some good spare parts (springs, pins, and that sort of thing) if you ever need them again.
There are people who sell legitimate full-auto weapons, and if you are interested in owning one there's a "full-auto / class III" forum here somewhere where you can learn more. A transferable machine gun is more expensive than Bubba's SKS and requires a little more paperwork to own, but in the long run it will be cheaper and less of a hassle than the fines and trouble the BATFE will bring your way if they even think you've manufactured or purchased a machinegun without their OK.
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