Cliffe, the .223 and .308 in F/TR are a military heritage. Main calibers in the Canada, Britain, U.S., Australia Armies. The U.S NRA, British NRA, Aussie NRA and Canadian DCRA evolved from military orginizations using Army ranges.
The F in F Class stands for "Farky" Farquharson, a Dominion of Canada Rifle Assocation (DCRA) shooter from the Province of British Columbia. His arms and eyes could no longer take Palma shooting, a sad fate for shooters from every country.
In the late 1980`s, the DCRA was experimenting with any sight, sling, any caliber much the same as U.S. NRA High Power Long Range. I actually shot in this demonstartion match at the Canadian Nationals in 1989 with a heavy barrel Ruger 77 .25-06.
This led to Farky suggesting in the mid 1990`s any sight with any front rest, rear bag, max 156 gr in .308. The class is called F(F), a Canada only class. International F/TR allows bipod only and any bullet weight, a situation that the DCRA must eventually resolve with the number of U.S. shooters coming to our Nationals in Ottawa.
The DCRA was (is) hidebound in Palma shooting with the .308, the military NATO cartridge. So the cartridge used in F(F) had to be the .308 with a max weight of 156 gr in case a 155 SMK actually weighed 155.2 gr.
The Canadian Army adopted the dreadful .223 cartridge in the 1980`s. The M16 clone, the C7, is made under licence from Colt in southern Ontario for the Canadian Army. So eventually the .223 was accepted by the DCRA as a Palma cartridge and hence an F(F) and F/TR cartridge.
There was a demonstration .223 match in 1989 at the Canadian Nationals (it still had not been accepted by the DCRA as a legit caliber) which I shot with a custom bolt gun with a McGowen barrel. My shooting partner was from the U.S. He had just come from Camp Perry.
So now the .223 is accepted by the DCRA as a legitimate Palma, F(F), F/TR carrtridge because it is the main Army cartridge.
I have no idea what tortuous route the .223 went through in the U.S. to be accepted as a legal NRA competition round. Probably something to do with Viet Nam and Iraq.
F(F) is slowly fading out in Canada, being combined with F/TR at the Nationals, any bullet weight , any front rest. Only two Canadians shot F(F) in the Nationals two weeks ago, both shooting .223. The U.S. Team Savage were not happy about the any front rest, an unfair advantage in their eyes.
So F Class continues to evolve.