An extra 2 inches (26 vs 24) shouldn't add that much weight to a rifle. The 7 mag would benefit from a 26" barrel. A 24" or 26" inch barreled rifle in 7mm mag., should be able to successfully kill a deer at 300 yards.

I have a older remington Model 700 BDL (24") in 7 mag and a Winchester M70 (26") in 7 mag. Which would I take to hunt deer, even at long distances? The Remington (24") because it pretty damn accurate.