As mentioned, simply fire factory rounds or handloads loaded to close to factory specs through it and your cases will be formed.
One thing about using handloads, it is often mentioned to seat the bullets into the lands in order to keep the cases snug in the chamber. With a properly chambered AI, you don't have to do this as the datum of the shoulder should fit with an ever so slight compression when you close the action.
I have a TC barrel chambered in .223 AI and for the life of me I cannot duplicate the accuracy I get from standard 46gr Winchester Varmint Pack ammo. In fact it shoots so well I don't even bother anymore. Box list velocity at 3600 and I am getting just over 3250 from my 14" barrel. I have a WHOLE bunch of formed cases ready to load, someday when I run out of it.