The interesting thing is, I asked someone at Criterion at one point last year, and I seem to recall being told that they were sold "finish reamed" and ready to fire after installation because there is no headspace issue.  Obviously a Garand must be reamed and timed with the bolt to headspace properly... but as everyone has already stated, the Krag headspaces on the rim. 

On a side note, I find it interesting that Criterion Krag barrels come "in the white" while Garand barrels come parkerized.