Welll..... I ran the .243AI for 7yrs trying to make it work. Many barrels, 4-5 rifles and 7 different chambering reamers later I switched ever'thang over to 6BR.
2 things stand out..........the .243AI will NOT make usable pressure before the primer pockets fail, they won't shoot like they "should". And the 40* shoulder makes for some unnecessary and insurmountable sizing problems. I still have 4 .243AI barrels, the only reason that I left them as .243AI's is because they're all professionally done with nicely engraved lettering.......all of my blank .243 barrels have been converted to 6BR's, two of them are scheduled for conversion to 6X47's for use as casual and fireform barrels and to test for velocity with the shorter length.
I have a .243AI barrel that's fluted and braked, cost me 500.00, now for something like that it's hard to just hack it off and start it over because the flutes are too long. I never use it, I screw it onto the action now and then just for varminting and to use it up. It's a Shilen and it's lasting very well.
The .243I is one of the coolest looking rounds on the planet IMO, I love the look of a big ol' moly-coated 107 seated 'way out even though I only shoot moly when it's convenient.
I now shoot my .243AI's neck-size only and when they get tight I throw the brass away. I've got it dialed down to where I can ramp up the pressure (107's at prox 3050-3100) and get the pockets to fail about the time the brass gets tight. I've taken the time to ream out the necks on two of them so that they're "no-turn" just because it's hateful to spend the time neckturning on throwaway brass.
I'm still in he design/development stage with the 6X47 but so far it shows all the attributes of the 6BR but will yield a couple hundred more FPS. It's like a blown out 6BR with a neck.
The 6X47 configuration is still in its infancy but I have no reason not to believe that it will prove to be a great all-around 1000yd and varminting round.
hth
al
