Just in case the video doesn't work, the inline clip does work, and is fully automatic. It fires about as far as a usual magstrike, and shoots about 3 shots per 5 magstrike air outputs (this video was a good one, and fired 3 for 3, at the highest possible ROF).
That makes sense now. I was under the impression that there was some sort of mechanism to load and fire a dart one at a time, which would function in either semi or full-auto. For clarification, is the "fully automatic" function based on the already existing components of the Magstrike? I ask this because I have used what is evidently known as an inline clip (loading several darts in a barrel), but the result was the expulsion of all darts at once as a shotgun, not in an automated, semi-predictable burst (the type of result one expects with the term "fully automatic").
I would guess that the results shown in the video reflect more of the mechanical function of the Magstrike, than the results of an inline clip in general, especially considering what would happen if there were a constant flow of air from the bladder to the barrel (mentioned above) as the Tommy Gun appears to be built for (unless I'm not seeing the rest of the Magstrike components). In that case the inline clip isn't really a clip since "clip," to me at least, suggests an ability to not only fire multiple darts in succession, but in a controlled manner either in semi or full-auto.
This is a cool homemade/modification, but I don't see how it's fully automatic.