Honestly, .223 remington is sufficient to kill a deer (fact) up to 200 yards (opinion). Maybe it has enough energy for further, but I'd have tho check the numbers. I'm sure many of you are currently scoffing, but the fact remains that .223 will kill a deer. Do you need to use the correct bullets? Of course, but this is the same for everything. Is shot placement crucial? Not a whole lot more than anything esle; gut shoot a deer with a .300 win mag and its still gonna run. Albeit not as far, but run it shall.
.243 is an excelent caliber. A hard hitting varmint caliber up to the "ideal" deer caliber. Also in this category is the 25-06 which has been said to have enough poop to bring down and elk, however bullet choices are very limited for the 25-06 on game this size. But you're not shooting elk (yet), so no worries.
In all honesty, I would probably get a 30-06 if I were you. Yes, I hear the scoffing again, but look at it this way: you can never have too many guns, ammo choices, including surplus, are very broad, AND the 30-06 will kill anything furry and good with bbq sauce in the United States.
I have to admit I am don't know much about the 25-06 or 7mm-08 calibers mentioned. Is a bolt action better than an automatic?
25-06 is a 30-06 necked down. 7mm-08 is .308 necked down to .284 (correct me if im wrong). Generally, the smaller the bullet, the faster muzzle velocity and flatter trajectory, decreased energy. I wouldnt worry about energy for yoties or deer at 300 yards. As far as automatic vs. bolt, the difference is in how the action grips the cartridge and holds it in the chamber. Generally speaking, bolt action rifles are more acurate than autoloaders. Some semi auto rifles can be very very acurate, but this drives the cost up. IMHO a semi auto is not needed unless what youre shooting at is running, or you tend to miss on the first shot and need to make a fast second shot before your prey is gone. However, I know some that swear by single shot rifles (falling block) due to thier accuracy. Besides, who needs more than one shot if you dont miss the first time
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Whatever you choose, shoot it a lot. Practice for deer on yoties, foxes, stumps, old freezers, birds, cans, targets, house cats, whatever you can find. The more you shoot your rifle, the better you will be at it.