[BattleRifleG3]

40 would no doubt be better for hunting than 9mm. Whether it would be good at all is another matter. Consider Ruger's 44 Magnum carbine if you want a semi-auto. Or a levergun.

Or a far better choice for a short range semi-auto hunting rifle would be the venerable SKS. Ammo is significantly cheaper, rifle is less than half the cost. For the same or better price ammowise and gunwise as a 40 S&W carbine, you could buy a CETME or Saiga in 308 (Saigas also come in milder calibers), good for all ranges of hunting deer sized game.