Also, a lot of 243/6mm carts burn a lot of power for not a lot more velocity. For example the 6mm Creedmoor uses 27% more powder to go 7% faster than the 6mm ARC.

Hornady sells some really nice factory loads for 6mm ARC at some great prices. In a bolt gun with handloads using CFE223 or LeverEvolution and 95-109gr modern high BC bullets its pretty easy to match the performace of most of the rounds mentioned. Again, except for 6mm CM which is a barrel burning powder hog.