if you look into some heavy bullet loads with a slower burning magnum hangun powder, you might be able to push the velocity high enough to perform well. I think with a bullet weight of 200gr plus and a velocity 1300+fps muzzle velocity it would work fine for deer provided you take a double-lung broadside shot and nothing trying to bust bones. perhaps a hunting bullet designed for the 10mm would be an appropriate bullet but i have no advice on loads except try and use a slow powder wo make use of that barrel length. though if this a lightweight plastic carbine from someone like kel-tec id be worried about damaging it with the heavier loads