I would like to see a DI gas operated AR upper in 10mm. The rounds fit fine in a standard AR magazine. They just have to pushed way to the back. A spacer could be made and the follower shortened and a spring that's not as wide (front to rear) 10 inch barrel with carbine length gas tube.... Should work. Need some mods to the bolt face.... ...
https://www.youtube.com/watch?v=JGH1uJFUivc
https://www.ar15.com/forums/ar-15/10mm_Gas_Op_Ar_15/15-390846/
https://www.youtube.com/watch?v=JGH1uJFUivc
https://www.ar15.com/forums/ar-15/10mm_Gas_Op_Ar_15/15-390846/