Of course I just built a 243 LBC last year...lol
Dan
I built two and have no regrets. The new cartridge may be available as a factory load, but I'd still shoot only handloads no matter what. One benefit is that there will at least be some data available that is close to 6mm AR...but the new factory round will have less case capacity and therefore more conservative max loads. At least we'll have another clue to consider.