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How to Adjust a Number 4 Peep Sight for a Mossberg Model 42B

The Mossberg model 42B is a bolt-action training rifle chambered to use .22 long rifle ammunition. These rifles were produced in the 1940s specifically as training rifles for the British military. The rifle utilized peep sights manufactured by Parker-Hale which were similar to the sights on the British Lee Enfield rifles (the primary battle rifle of the British army during the Second World War). The peep sight featured two adjustment knobs which allowed the rifleman to adjust the sights without special tools.

Things You'll Need

Target
.22 LR ammo

Instructions

- 1
  Determine the amount of adjustment needed by carefully aiming your rifle at the center of your target and firing at least three controlled shots.
- 2
  Check your target and mark the center of the shot group and estimate the required adjustment. For example, if your shot group is 1 inch below and 1 inch to the right of where you where aiming, and you need to move your sight 1 inch up and 1 inch to the left.
- 3
  Adjust the knob on top of the peep sight to make changes in elevation; the sight is calibrated for one click to change the sight 1/8 of an inch on a target of 25 yards. Likewise, adjust the knob between the sight ladder (the post of the rear sight) and the peep sight to control the horizontal movement (in the same increments).

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