The model 721 was produced from 1948 to 1962
I'd get in touch with Remington. They can tell you. I would expect that it's possible, as they should be pretty interchangeable, however, it would be unlikely.
Actuate the bolt to the rear and there is a tang in front of the trigger that hangs down..Press up on this tang and pull the bolt back and it will remove it from the action.
The Remington Model 721 in .300 H&H was manufactured in 1948 with a 24" or 26" barrel.
100-400 or so
100-300 USD depending on condition.
If it is in 100% new condition and unfired, it could be worth around $700.00.
1 in 10
100-300 USD
General information on the 721 can be found on the Remington website here: http://www.remington.com/library/history/firearm_models/centerfire/model_721.asp
Your Remington model 721 was produced from 1948-1962. If you can supply the 2,or 3 letter code on the barrel we can pinpoint the month and year of production.
NOTHING............Its a Remington