A couple of friends of mine have .220 Swift - thats a lovely cartridge. Basically zero recoil but with tremendous velocity and accuracy. You can get ammo for it but its hard to find and when you do find it its pricey, so reloading would probably be a good idea.
.22-250 has about the same energy as the Swift but in a short action cartridge. Ammo is easier to find but I have heard it is nice to load for.
Others are .222 or .223 - Less energy than the Swift or .22-250, easy to find ammo for and nice to reload for. Another mate of mine reloads for his .223 AR and love it.
Having fiddled about with some reloading and just found a good load for my .300WM (because I use this rifle for range work as well as hunting and bugger paying £40 a box for ammo and then blasting through two boxes on a Sunday morning) my advice, albeit far from expert advice, would be:
1) Always full length size your brass. Dont bother just neck sizing as eventually the shoulders will come out and your rounds will start to jam in the chamber. JMHO and all that.
2) Personally I haven't found any benefit from faffing about with COAL. Hunting rifles seem to have fairly long throats so they can accommodate lots of different ammo so I just load to SAAMI max length and leave it at that.
3) If your charge weight range is 40-50gn of powder then just load one of each load at 40, 41, 42, 43, 44 and 45 (as you're very unlikely to be over pressure at the bottom part of the range) and then go up in 0.5 grain increments from there. These loads are purely to check for pressure signs not for accuracy. Shoot these before you start testing for accuracy.
4) Assuming you have no pressure signs at any charge level (which hopefully you wont) then I tend to load three to five of each from the mid range charge weight to max load and check these for accuracy.
5) Most factory ammo will give you 1 MOA accuracy so as long as your home loads are giving you 1 MOA or under you're doing well and this will be more than accurate enough for hunting. Hopefully you'll get sub MOA accuracy.
6) Factory ammo is a good guide as a place to start when you start loading. If your rifle really likes 150gn .308 factory ammo then starting out with 150gn bullet heads is probably a good bet.
Hope thats of some use!