Entire books have been written on the SMLE. Try your local library or do a web search.
Google the phrase and you will get hundreds of hits.
Using blueprints.
An SMLE rifle comes in three types: SMLE Mk III - 1132mm / 44.57" SMLE No. 4 Mk 1 - 1129mm / 44.45" SMLE No. 5 "Jungle Carbine" - 1003mm / 39.49"
303 was the .303 inch diameter bullet that was fired by the Short Magazine Lee Enfield- or SMLE. Standard rifle of the British military from 1907 to the1960s, and still in limited use today.
Depending on the exact model and condition, anywhere from $100 to 400.
Depends on which model (that was the overlap period between the MLE and SMLE, if I recall) and value will be driven by condition and originality- a sporterized rifle has a sharply reduced value. A SMLE in good condition may be worth $150-250. Excellent condition may double that.
2441 feet per second when fired from the British SMLE rifle. Velocity will vary when fired from rifles with a longer or shorter barrel.
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.
".303 British" is usually used to denote a caliber, as opposed to a specific firearm. Perhaps the most famous rifle in that caliber was the SMLE, which is the abbreviation for Short, Magazine, Lee Enfield. There were several marks and models of British military rifles that originated under that designation, all in that caliber. They were made from prior to WW I, and continued through the Commonwealth nations (and former Commonwealth nations) into about the 1960s. So, yes, the caliber .303 British and the Enfield name are linked- but Enfield is not the full name of the rifles and carbines. Run a Wikipedia search on SMLE for some more reading.
Moderately scarce. The SMLE 1 was produced 1904-1926, making yours a first year production rifle- but they did make a lot of them.
Where it was made, proof marks, etc..
SMLE- aka the Lee Enfield