The AI chambers are designed to be chambered slightly shorter at the juncture of the neck and shoulder than the parent standard cartridge, ~0.005" or thereabouts IIRC. This is so that a factory cartridge would be safe to fire in the Improved chamber without any risk of a head separation. You are SUPPOSED to have a slight difficulty in closing the bolt on a factory cartridge but perhaps not THAT much difficulty(G), hard to say without a hands-on.
This is the reason that most smiths will insist upon setting the barrel back a thread when rechambering to the AI configuration, in order to achieve this very slight reduction in headspace.
Regards, Joe
