From time to time, I think it is a good idea to describe "F" class; what it is and where it came from. Although it's a fairly new sport, there have already been enough changes that it now has a "history". The "F" in "F" class stands for Farquharson. The class was originated by a Canadian target shooter by the name of George Farquharson. George saw "F" class as a venue which would accomplish three goals. First; by opening up the range to calibers other than the 7.62 and 5.56 and by allowing "any rifle, any sight, fired from any rest" it would serve to attract new shooters to the sport of long range shooting. Second; the use of scope sight and a rest would foster experimentation and improve rifles and sighting equipment. Third; the use of optical sights and rests might extend the competitive life of some of the older shooters of which George, in his eighties at the time, was one.
So it was that the original rules were for any rifle (weight limit 10KG), any sight, and fired from any rest. If a bipod was used, it counted as part of the weight of the rifle. Any caliber up to 8mm was allowed.
In the early years of "F" class competition we saw all sorts of rifles on the line. As time passed "F" class kind of split into two camps. One camp was the "benchrest without a bench" contingent. They used rifles which were essentially 1000 yard "light" rifles in various calibers with the 6BR and various 6.5's being favorites. The other contingent were of more the "target rifle with a scope" camp and they usually shot 223's and 308's in target rifle configuration. Eventually two classes resulted. One class, the "F"(O) class is open and the rules for the rifles are as originally set forth by George Farquharson. The other class became the "F"(TR) or in some venues the "F"(f). The rifles were restricted to two chamberings, 308 or 223, and some regulations were put into place regarding rests etc. So it is that what George had originally intended as a wide open, fun competition, has become more and more complex.
Personally, I would prefer to shoot a 308 over a 223 but if I was to shoot a 223 I would build it with a 7.5 twist barrel to shoot 80 grain bullets. Since 223's have to work at pretty high pressure levels, I would be sure and choose an action with a 1/16" diameter firing pin tip to help eliminate blanking of the primer. I believe the weight limit for "F"(TR) is 8.5KG which gives one a lot to work with; even with a fairly heavy bipod. The one thing which is nice about the 223 is that it is easy to shoot. No recoil means it won't fatigue the shooter like a 308 can.
BY the way, the course of fire varies from venue to venue. In Alberta they generally shoot from 300 too 900 meter in 100 meter increments. This is a neat course of fire; especially when they mix up the ranges. You have to know your rifle. Other matches are fired at whatever ranges are available with some limited to 600 meters. Occasionally there are special 300 meter matches fired on the ISSF target. 100 rounds, twenty per target.
Other matches may follow the Palma course from 700 to 900 meters or 800 to 1000 yards. GD