Hi Seb,
Lets back things up a bit. You're an engineer, right? And you know that every product involves compromises. Design, material availability, cost, on and on. Point 2 is that an internet forum best serves specific things. It can't replace a book: too little space, to little time to check that the writing is both sound and complete -- esp. complete.
OK, your original requirements were : 30 caliber, .308 boltface, potential to win at both 500 meters and 1,000 yards, while shooting in formats where those restrictions are not generally there. Answers given, by me at least, respected those initial compromises.
There are still compromises. An F-class rifle, as I remember, can weigh 22 pounds, but cannot have a muzzle brake. A 1,000 yard IBS/NBRSA/Pennsylvania 600 yard or 1,000 yard Light gun can have a brake, but is limited to 17 pounds. I have no ideal about equipment restrictions in the Fly.
There is an old rule of thumb about 1,000 yard shooting: a MV of 3,000 fps and a bullet B.C. of .500. You can trade one for another -- higher BC (less bullet drag), less velocity needed. It's a guide only. The 6BR, right at the bottom of this formula, is doing quite well.
OK, a 17-pound, 30-caliber rifle without a brake is not a lot of fun to shoot. Well, 1K NRA prone matches use to be shot with .30 magnums, it can be done. Those rifles had less weight, too. But it wasn't fun, hence the move to chamberings with less recoil. The extra weight of F-class helps, but it is still in the serious compromise region.
What Jeff is suggesting is reevaluate the .30 caliber design restriction. If you do so a whole lot of other solutions open up.
A 7mm is a slightly smaller hole. Recoil with 168 or 180 grain bullets is still up there. But, with a .472 boltface, there are several chamberings that are seriously competitive: the .284 Winchester, the .280 Ackley, the newer Remington short guy (not quite as big as a .280 Ackley), maybe even a 7x57 Ackley, which has a larger capacity that the 7mm/308.
As I said in an earlier post, as the hole gets smaller, 6.5 or 6mm, choices open up. A lot -- enough so that a whole other set of compromises come into play. But these are "fine-tuning" compromises, a different order of magnitude that the original set. 6BR versus 6mm Dasher versus.243 Ackley versus 6 Ackley -- those sorts of things.
As to the .284 case: the .284 Winchester was developed to get a case of .270 like performance that would function in the (1960) newly designed Winchester lever and autoloading rifles that were quite strong, but needed a case shorter than the .270. It is about 2 inches long, and has a body diameter of about half an inch. Little body taper. Shorter neck, sharp shoulder, rim rebated to .472. The capacity of the case is almost dead on the same as a .30/06 -- or .270, its original design goal.
There is no doubt in my mind that a plain .308 will work at 500 meters. For a time, anyway, the IBS small group record was held by a .308 in 600 yard Heavy Gun benchrest class. Maybe it has been broken in the past two years, I dunno. But it is seriously competitive.
There is little doubt in my mind that a .308 gives up too much at 1,000 yards to be competitive against other chamberings, except where the rules prohibit them, as in F-class T/R. But as I also said, the guys who know the "fine-tuning compromises" of the .308 hang out on different forums.
Finally, you seem to be adding another constraint: a reamer that your Australian gunsmith might have. How would we know? An I'll mention some more issues: components that can be exported from the States. The U.S. government has raised the fees for the licenses needed to export components to the prohibitive level. Only large suppliers can afford them, and large suppliers don't carry "exotic" stuff, like BIBs bullets.
What I really think is that in order for us, on an internet forum, to be of much help, you need to get with your gunsmith, the fly shooters etc., and narrow things down. It isn't that we're unwilling, it is just the range of stuff gets too big for a post-to-the-internet forum.
