Any cartridge that is accurate at 300 will be accurate at 800, it is just a matter of reading the wind. Your "experts" will likely tell you to go ahead and build the 7rm because that'll guarantee them some work in the near future. Sure it can be an accurate cartridge but so can alot of other cartridges. I'd say just go and shoot your take down rifle against other 308s. If it is nearly as good as you say it is and you're as good as you claim to be then you'll definately be coming home with some trophies. If you have your heart set on building a gun, go with one of the many board sponsors that. Theyre here for a reason, they love shooting as much as we all do and any work we can give them will give them a reason to stick around.