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.
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.
100-400 or so
old, obsolete rifle, bout $300 US if its in good shape
You can request a owner's manual at the Remigton web site.
100-300 USD depending on condition.
The made them from 48 - 62, they are date code stamped on the barrel, the location and chart is on the Remington Society of America.
The model 721 was produced from 1948 to 1962
The Remington Model 721 in .300 H&H was manufactured in 1948 with a 24" or 26" barrel.
I just purchased a model 721 in 300 savage caliber and paid 325 dollars for it.These are fine examples and mine shoots great.For the money you are getting a well made rifle and piece of history.Enjoy it my friend.
If it is in 100% new condition and unfired, it could be worth around $700.00.
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