Hm hm hm. Looks more like 26mm shotgun/mini warhead semi-auto. Handle connected right to barrel space which is a bit awkward but overwall everything in it's place. Except maybe optics mount is too high.
Neat design!! This reminds me of the french FAMAS assault rifle crossed with a grenade launcher. What exactly is a "nade rifle"? Is it just a name, or does it shoot nades (whatever those are?). Perhaps nade is slang for "grenade"? Perhaps secret grenade tech?
That's a drum magazine, I'm guessing? One improvement I might make would be to raise it, slightly, and either extend the receiver to go a little past the front of the magazine or move the magazine back a little. As it is the feed system would be more complicated than it has to be. Other than that it looks great! The barrel even looks a bit like it has an integral suppressor, which is pretty cool.