e. Headspace Adjustment With the Gage. With the gage, you can accurately determine the distance between the face of the bolt and the chamber end of the barrel by the following procedures:
(1) Raise the cover. Retract the recoiling parts as described in paragraph la, and screw the barrel all the way into the barrel extension, then unscrew the barrel two notches.
(2) Cock the gun; pull the retracting slide handle all the way to the rear, then return it to its most forward position. Press the bolt latch release and allow the bolt to go forward.
Note. Be careful not to depress the trigger, since this will cause the firing pin to be released.
If the firing pin is forward, the gage cannot be inserted in the T-slot far enough to give an accurate determination.
Caution. The firing pin should never be released with the gage in the T-slot as this could damage the firing pin and gage.
(3) Pull the retracting slide handle back until the barrel extension is about one-sixteenth of an inch from the trunnion block. This will insure that the locking surfaces of the breech lock and the bolt are in proper contact. This prevents the driving spring group and weight of the parts from giving a false determination (fig 81).
(4) First, insert the GO end of the headspace gage in the T-slot, between the face of the bolt and the rear end of the barrel. If the GO end of the gage enters freely down to the center ring of the gage, then attempt to insert the NO GO end of the gage. If the GO end enters, and the NO GO end does not enter, correct headspace is set.
(5) If the GO end of the gage does not enter freely, headspace is too tight. When this condition exists the barrel must be unscrewed one click (notch) at a time (checking with the gage after each click), until the GO end of the gage enters freely. To complete the adjustment, attempt to
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