>>64017596
There are a shit ton of 30mm STANAG calibers but the least unfeasible thing for 30x173 is probably the Oerlikon KCA/KCE.
It's technically not a rifle but an automatic revolver, like most autocannons.
It's only 136 kg unloaded so yeah it's basically man-portable home defense weapon. Recoil? Nah don't worry about that.

(The madlad responsible for Maadi-Griffin anti-materiel rifles actually prototyped one in 30x173mm but for obvious reasons it didn't pan out)