![]() ![]() Hold the back of the locking piece and the front of the bolt head with the thumb and index finger of one hand. Insert the locking piece into the bolt head.While holding both rollers inside the bolt head with your thumb and pointer finger of one hand, flip the bolt head right-side up with the roll pinhole facing up.Repeat on the other side with the new roller on the exposed retainer plate dimple exposed.Carefully push the roller into the bolt head. Place the new roller onto the roller retainer plate with the recessed side of the button facing the detent.Slide the roller retainer plate into the recessed channel with the detents (buttons) side up.Remove the rollers and roller retainer plate (roller holder).Tap the bolt head until the roll pin falls out.Using a 5/64 inch roll pin punch and hammer, drive the roll pin into the body of the bolt head.OPTIONAL: replacement roller retainer plate (roller holder) in case original one breaks - note that there are different generations of roller retainer platesįrom a disassembled weapon and bolt head removed from the bolt carrier assembly:.OPTIONAL: replacement roll pin in case original one gets damaged.2 replacement rollers (one size lower or higher to adjust bolt gap accordingly).Record the measurement once a firm drag is obtained on a gauge.Turn the weapon upside down and insert a feeler gauge through the magazine well into the gap between the bolt head and bolt carrier.Put the selector on semi and press the trigger, allowing the hammer to fall.Point the weapon toward the floor, release the bolt and let it snap forward.After the function check, the bolt is to be locked to the rear. Assemble the weapon and do a function check.How to Measure the Bolt Gap Tools Needed:Īlways clear the weapon before doing a functions check! The further the locking piece moves in, the smaller the gap gets. As the locking piece moves, so does the bolt carrier. ![]() As wear occurs in these areas, the locking piece is allowed to move further into the bolt head. Excessive wear will change the timing of the rifle and result in malfunctions. Bolt Gap Range Bolt Gap RangeĠ.010 inches (0.25mm) - 0.018 inches (0.45mm)Ġ.010 inches (0.25mm) - 0.020 inches (0.50mm)īolt gap is measured to check the wear of the rollers, locking piece shoulders, and barrel extension roller recesses. The distance between the rear of the bolt head and the front of the bolt carrier WHEN the bolt is IN battery and the hammer forward. Video instructions by James of Zenith Firearms.Always clear the weapon before doing a functions check!. ![]()
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January 2023
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