$50 to over $1000, depending on what exactly you have; i.e., make, model, arsenal, distinct markings, overall condition, etc. The question as is would be much too vague to give a more specific answer than that.
100-1000 USD or more depending on specifics
Assuming you mean a British MILITARY rifle, such as the SMLE, between $100-$350, depending on condition and originality. Rifles that have been "sporterized" lose much of their value as a collector's item.
yes there is a springfield .303 i have one from 1942 its a springfield rifle with a .303 british barrell
number5 mark 1 enfield 303 british jungle carbine
50-250 uSD
yes it is just a difreint mesherment 303 is british and 7.7 is jap.
What is my 303 savage model 99 worth?
British 303
100-1000 USD or so depending on specifics
Assuming you mean a rifle in caliber .303 British, and not the ammo- depends on which rifle, and its condition. A SMLE (#1 Mk 3) or a #4 Mk 1 may be worth $100 for a poor condition rifle, or $350-400 for an excellent one. The TRUE Jungle carbines have their own values (many counterfeit copies) and other models different values. Rifles that have been "sporterized"- converted from standard military configuration are worth much less.
Combination of serial number and features.
50-300 or so
No, a 303 is a rimmed cartridge, the 308 is rimless.