I'm not even worried about "stepping on toes" with this post, I'll give you my straight opinion, which agrees with some of the other posts, and it's based on shooting caribou, and seeing a number of others shot on hunts.You pretty much have every game covered, within reason, with your three guns. The .243 I'd leave at home on this hunt. You DO NOT need the .338, take it if it's your favorite gun, you like carrying it, and you shoot it well, but you are going WAY over-gunned for caribou. The .308, since it is already in your arsenal, is the gun of choice here, especially since you say you reload, as you have a ton of options. All of the bous' I've killed have been with the .308 with a 150 grain Hornady BTSP Interlock, and all dropped easily. If you are worried about the .308, which you have no reason to be, jump up to a heavier game bullet, many have been suggested, but you really don't need to. As was mentioned, these animals tend to be over-rated in size, partly because of the large rack and large belly, both of which make them look bigger. On all of the hunts I have been on, I don't remember anyone hunting with anything bigger than a 30-06, and with good shot placement, key on anything you're hunting, the caribou does not require anything more. Also, as mentioned in other posts, weight on a long day's hunt is important, good (waterproof!) optics are a must (scopes, rangefinders, and binocs). Wind is often a constant companion on the tundra, plan for that as well. Get your lungs and legs in shape prior to the hunt, and GOOD LUCK!! One more thing, when you get one, don't wait too long to gutit, their stomachs are designed to "chew up" the lichen they live on, as soon as they drop, their stomachs start swelling and become green slurry time bombs, be VERY careful with your knife....you have been warned![:'(]