I had a gunsmith tell me that most of the time the headspace will be within acceptable limits, but the logos and stamps on the barrel won't be timed correctly. Of those that were too long, he thinned the recoil lug.
I took off a 243 barrel and installed a 308 barrel. It would just close on a no go gauge. I disassembled it and thinned the recoil lug until it would just close on the go gauge. It is accurate and has worked well for redneck gunsmithing.
The only problem will be if it won't close on a go gauge. Then the chamber would have to be reamed.
