I have used both .223 Rem and .308 Win rifles in F-TR for well over a decade. They both have their place in the sport, and I would generally advocate that deciding between the two is up to the individual, and should be strongly influenced by the user's relative amount of participation in mid-range versus long-range F-Class matches. I personally would never advise someone to use a .308 Win with 155s in F-TR matches. That's a good recipe for learning how to lose against shooter using more realistic bullet choices, and it's simply not going to prepare someone for the gun handling skills they will eventually need with heavier bullets and stouter loads. Nor will the wind-reading hold-offs they start commiting to memory be correct. So going that route will eventually mean re-learning quite a bit. If you're going to use a .308, my advice would be to use it exactly the way you plan to use it in matches, meaning the exact same loads with which you plan to compete. Anything else is a waste, IMO. FWIW - if you're not going to start out or practice with the same load you ultimately intend to use in matches, what's the point? Over the long haul, that approach may seem to be a good idea, but in reality it can be a huge cost in both money and time. In that event, a .223 Rem with 90 VLDs will not just outperform 155s by a little bit, the difference in windage would be substantial, on the order of ~0.2 MOA at 600 yd and ~0.5 MOA at 1000 yd.
