Is there a big difference between a 223 rifle and a 270 rifle?

Answer 1

Yes, a very major difference. The .223 Remington was designed from the ground up as a varmint cartridge, with its origins in the .222 Remington and later the .222 Remington Magnum. The .270, on the other hand, is intended for larger game - it is essentially a .30-06 cartridge, necked down to accept a smaller projectile.

It's a matter of physics and basic ballistics. The .223 is at least half the weight at 55 grains and on most loadings is somewhat slower than the .270 cal. The .223 will have less penetration power at equal distance and more perceived drop, because it takes more time to reach the target. At close ranges, the difference will be minimal, but as the range opens, the differences become more apparent. Both will kill with proper aim, but the .270 is far more able to handle larger game with it's higher power and flatter tragectory.