I realy don' t want this to turn into a pissing match but the .223, .222. 221 fireball and .220 swift are not deer calibers. Yes you can kill a deer with one and you can kill a grizzly with a .22 short if you want to bad enough. Most states it is illegal to use under 6MM ie .243 cal. The reasons the larger calibers work better is bullet coefficent, retained energy and cross sectional area. This is an example I use for Hunter Ed. classes;

You have a Corvetee that goes 300mph and run into a building. Now you take the same building run into it with a Peterbuilt traveling a 100mph, which would cause the most damage and achive the most penetration. The Peterbuilt would. Why? Because the corvetee would break down, and lose all it' s energy in a very short distance where as the Truck would plow through and causing massive internal damage and possibly a pass through. Lighter weight balls lose thier energy faster. Pure Physics.

Accuracy is a very important element in any hunting sittuation, But it' s only a portion of the whole picture. You can blow a shot with a .600gr 45/70 just as quick as you can with a 90gr .223 but there is much larger margrine for error with the large caliber. By this I mean if you have a high wind say 20-25mph blowing left to right how much farther to the left do I need to hold the .223 than the larger calibers. Like I said; this is what my opinons are and that' s my nickel' s worth.