Defense Distributed announced that their 3rd generation of 3D printed lowers is ready for distribution. No one knows what the expected life of this lower will be, as it has been used to fire 600 rounds in rapid succession without discernible damage.
In the video, right and left handed shooters switch places while firing the test rounds in rapid semi-action mode. It is clear that the shooters are starting to suffer from hand fatigue from so much trigger action.
The lower receiver design has been reinforced. The upper used is a direct gas impingement type. I would expect that a piston driven design would also work, and might create less potential problems as there would be no hot gases ejected into contact with the lower receiver.
No one knows what the service life of this receiver will be, but 600 rounds without detectable problems is a good start.
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