[1] It was produced in several different versions until World War II, when shortages of materials made production of a training rifle impractical.

This version had a new bolt head, an improved firing mechanism, modifications to the chambering, and a new rear sight.

the main distinguishing change in the M2 variant was the incorporation of an adjustable headspace mechanism in the locking lug.

This mechanism consisted of an Allen key screw that passed through the locking lug bearing against the right rear receiver wall.

If the eagle was disturbed the armourer would know that an attempt had been made to change the headspace by unauthorised personnel.