Hey TJ. There's a few on here that are being unnecessarily rude, but for the most part, you gotta take your licks where licks are due. The caliber differences that confounded you are clearly covered in the PAL course book, so I can understand some folks SMH response.
Anyway, moving forward, here's a few resources for your future use:
Here's a link to a variety of common pistol and rifle cartridges, and their respective diameter in inches:
http://www.dave-cushman.net/shot/
Here's a pic of some of those for comparison's sake:

Hope it's not too blurry :-/
Alternatively, you can also just take any caliber in "mm" and multiply it by .03937 to get the caliber in inches. Conversely, you can take any caliber in inches, and divide by .03937 to get the caliber in mm. I should note though, that these are approximates. Cartridge calibers are names, not diameters. Yes, they'll be close, but bullet diameters don't always line up with their cartridge names. For instance, your .308, if measured, will actually be closer to .311 (if I'm wrong, the reloaded a will be by shortly to correct me). It's not a big difference, but something to be aware of anyway.
Lastly, here's a (very) simplified chart of what cartridges suit which game. I post this at my own peril as there are thousands of threads on here arguing about the suitability of caliber X for game X. It's a loose guideline at best, but a place to start nonetheless.
I hope that helps a bit.
KJ
Ps. A lot of folks (myself included) set a "kinetic energy delivered at range" threshold for themselves. That is, they pick a number of foot pounds or joules as their ethical limit for for a certain type of game. For instance, my self-imposed limitation is 1000ftlbs for all large game (save grizzly). Kinetic energy depletes rapidly as a bullet travels down range, so I set my maximum range limit at the point my bullet's kinetic energy drops below 1000ftlbs (or where my accuracy drops off, whichever's shorter). So with something like an SKS, I wouldn't shoot game past 125 yards. With something like a .300 mag, it's kinetic range far out reaches my accuracy range so it's my own competence with the rifle that sets the range limit. When it comes to handgun calibers, there's not much that meets my limits. Not to say that a 10mm carbine like this beauty wouldn't fit the bill
http://www.canadiangunnutz.com/forum/showthread.php/1375502-10mm-Takedown-Carbines! but that's up to each individual Hunter.
Pps. Spend a little extra time in the hunting regs if you're looking to get a pistol cal carbine. Many come with 10 round pistol mags (legal) but if you province's hunting regs specifically limit "centrefire rifles" to 5 round magazines, then you'd need to abide by that when hunting to keep yourself out of hot water.
Cheers.