No doubt Mossy.
Remington is a manufacturer of firearms.
300 & 7mm, when refering to cartridges, can be a whole lot of different cartridges. The bullet diameters are .308 inches for the 300 and .284 inches for the 7mm. That is only a differance of 24 thousandths of an inch.
For instance you have a 300 winchester magnum, 300 Savage, 300 Weatherby magnum, 300 Winchester short magnum, 300 Remington ultra magnum, 300 Remington short action ultra magnum, 300 Whisper, 300 H&H magnum, and so on and so on.
Here are a few 7mm's... 7mm-08, 7mm Remington magnum, 7mm Weatherby magnum, 7mm Mauser, 7mm Remington ultra magnum, 7mm short action ultra magnum, 7mm Dakota, 7mm Winchester short magnum, 7mm shooting times western, and so on and so on.
If, however, you are refering to the 300 Winchester magnum and the 7mm Remington magnum the dead animal will never know which one you used. As far as power, trajectory, and effective range for killing animals they is no real world differance.