I don't shoot FT/R, but service rifle shooters shoot 600 yards with a 20 inch barrel, so I would guess you would be ok with a 26" barrel. I'm just guessing, however.
I don't know that there are any spotting scopes that have the resolution to show .223 hits at 600 yards. At that range, we are talking about the ability to resolve an object with a diameter of approximately 0.037 minutes of angle. I have a Kowa Prominar TSN-3 with their flourite Prominar lenses and it won't show that. (That's why there are pit workers who mark the target with spotting discs in high power competitions)
Unless FT/R is very different than high power competition, you will want an angled eyepiece. You will be behind your rifle and will want to glance through your scope with minimum movement and without breaking your "locked into your rifle" position, an angled eyepiece works best for that.
I googled "FT/R shooting prone" and found the following image. Notice the scope on the far side of the rifle (I think it's the same one I have, actually) and the angled eyepiece set up so the shooter can simply lean/incline his head just a bit, and look through the scope without breaking his position.
Bookmarks