I have an opportunity on a Texas exotic/hog hunt. I get the idea that using a rifle will be like shooting "fish in a barrel" and I would like to try something more challenging. I also can't afford to purchase a new firearm right now.

I have a Ruger 357 with a 4 inch barrel. Whatcha think?

For small hogs it's adequate. For head shots it's adequate. Problem is that head shots don't always present themselves and you may encounter a big hog in which case you should probably use a bigger caliber. Have you handgun hunted before?

I have never handgun hunted.

Get some heavier weight (i.e. 180 grains) bullets and go forward. The exotics won't shouldn't stop those bullets, so be careful of what is behind them when you shoot. Talk with your guide, most likely he'll have something to back you up if need be.