Arbiter 450 Bushmaster - Sawed off AR

Technically this model of gun was... can shooter, but no one really want that so I modified tube to be semi-supressor-handguard and put there 450 bushmaster, because its just nice caliber for such weird gun.
Originally at the end of the grip there was some visible buffer tube but I realize that there should be no problem to cut it off and hide totally in grip for such big caliber...

There is also Fightlite SCR Pistol but its normal sawed off AR, and I wanted that weird can-suppressor-handguard.