F-class is Mid Range (300 to 600 yards) and Long Range (800-1000) target shooting with scope sights and artificial support allowed, unlike NRA Conventional shooting. It started in Canada as a means of keeping older shooters in the game after they (we) started having trouble seeing iron sights and getting trussed up in coat, glove, and sling. It has spread to the US, is now supported by NRA, and is often seen here as a way to get new shooters started with their wannabe sniper rifles as well as keeping the codgers shooting.
There are two subdivisons, F-T/R (which they say means "target rifle" but we know means "tactical rifle" because it is limited to the service calibers of .223 and .308.) Must be shot off a bipod attached to the gun with a rear sandbag allowed, weight limit 8.25 kg (18 lb) scope and bipod included, no limit on scope power, any safe trigger pull, any safe load.
F-Open rifles can be any caliber under .35, shot off any rest as long as it does not return the gun to battery and does not connect the front and rear rests, weight limit 10 kg (22) lbs, not including the rest as long as it is not attached to the gun.
NRA got worried about perfect score ties with rests and big scopes and cut the target size in half last year. The F target now has a one-MOA ten ring, that's 10" at 1000 yards.
You can dig out some stuff on the NRA site
http://www.nrahq.org/compete/index.asp
and on the Long Range board
http://www.long-range.com/forums/
including ranges in your area.