I've had a couple of 243 AIs,Still have one and like it.
That being said, I'd go 6mm Creedmoor if starting from scratch
My situation and thoughts as well.
I've had two barrels chambered to .243 AI, one factory and one after market, and it's a fine round. Both barrels were very accurate, the Pac-Nor custom was and still is capable of putting three shots into the .2's consistently but that's probably as much a testimony to the barrel maker as anything. My sort'a scientific test using the same barrel in .243 and .243 AI showed that rechambering reduced throat erosion by about 10% compared to the parent .243.
However, the 6mm Creedmoor doesn't require fireforming, has excellent brass available, is throated properly and gets the same speeds.
Now having said that, when the current barrel is toast I may just continue to go with the .243 AI because I paid for and still have the reamer and go gauge, but that's just my case. If I didn't, I'd go 6mm CM all the way.
