.223 Remington for white tail? Irrr..... OK, I'm better now.

.223 is just not suitable for white tail unless you are talking one of the tiny subspecies that you find on islands and such. It doesn't have the energy on target you need to put it down and not destroy a bunch of meat. A .30-30 or 7.62x39mm is really the lightest I like. You can go smaller, but it has to be faster; .243/6mm is about the smallest bore I'm likely to suggest.

In those weights, I suggest for most people a box-fed (detachable or internal, doesn't matter) pump or bolt action with a barrel not much over 20". If you want to go ultra-light, a good break action IS lighter, but it's defensive applications are very limited. (You picked a USP for your sidearm, so I'm guessing you want something with a defensive role.)

That being said, looking for deer might not be the best use of your time. You are more likely to find something smaller. There are ways to do this with a bigger rifle- adaptor cartridges, which let you fire a lower powered, usually pistol, cartridge of the same caliber from a bigger cartridge's chamber. .30-caliber is pretty much a must now. For example, I have adaptors for .30 Carbine into a .308, and 30 Mauser/Tokarev in .30-06. Or you can get someone to light load something for you. But, you will never have the right found in the chamber, and small game will be gone by the time you have the right one in. And adaptors have little finicky, easily lost bits, while cold loads look pretty much the same as a normal load.

Instead, I suggest a good .22. I own an AR-7, and I like it, but I accept it isn't as accurate. If I have the bulk, I'm more likely to select a simple bolt action .22LR or possibly a .22 Magnum. .22WMR would give you bunnies, woodchucks, muskrat on the beach, and the like.

And both of them are better if they hit in a fight than if you miss with a better round. .22 is a fraction of the cost of a the bigger centerfire rounds, which means you can practice more.

The best compromise round would be a hotter handgun round in a carbine. I like .44Mag, but other than the Ruger bolt action carbine, AFAIK there is only lever actions and breaks in this round. (Sorry, I just don't have the same faith in lever actions for durability as a lot of people do.) With a good softpoint, it will thump deer and small bear out to 50m, and if you can head shot or have lighter rounds you can bag bunnies and the like easily enough. (I might have the bunny round in the chamber, then the hotter one under it, so for bigger, slower, easier to hit things, you have a proper round pretty much at hand. But you have the same problem with the rounds looking a lot alike.)