I'm sure there are a lot of people here that can list lots of differences between the two. But Remington used to make 721 and 722, a long and short action. They changed and called both of them 700... basically they are the same... The spring for the bolt stop has changed, the bolt handle, the trigger, trigger guard and probably more, but 700 stuff usually fits 722 or 721, after market stocks, triggers all work.
jimann