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Bizarre; his web-page shows what looks like a "combo-Luger" with a Walther GSP (with a Thompson pistol-grip) built into the forearm of a Luger carbine.
Realistically, it's probably built on a Russianb Capture mismatched POS Luger that had a shot-out bore to begin with, so I say Why not?
I think he needs to figure out a better feed system than Luger mags though... a Trunnelmag would be a good start!
Actually, Luger (ie, DWM) made some sporting rifles based on the Luger action back in the pre-WW1 days. Those rifles are ULTRA rare and expensive now though.
Oddly, the Luger action is sort of copied from the Maxim Machinegun action, albeit heavily modified... so it can be adapted for rifle and machinegun use!