Depending on the condition (stock, metal, etc.) and the sights it has, anywhere from $250 to $600. Most average condition ones are in the $300-$400 range.
100-300 USD
100-400 or so
1 in 10
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.
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.
It all depends on condition, box, manual, accessories, etc.. Range 175-400
100-300 USD
NOTHING............Its a Remington
Diagram and table on related link
old, obsolete rifle, bout $300 US if its in good shape