Changing A No4 Lee-Enfield Back Sight.
1. Safety first. Ensure that the rifle is unloaded. Remove the magazine and the bolt from the rifle.
2. You will require the following tools for this job.
a. A small hammer.
b. A pair of thin nosed pliers.
c. A small (approx 1mm tip) drift or punch.
d. A 3mm tip drift.
e. A thin bladed flat point screwdriver.
3. Lay the rifle on the bench with its right side down. Ensure that the back sight is folded down and identify the cross pin which the sight rotates around. At the end of this pin (on the left of the rifle) will be a very small lock pin which holds it into the rifle body. Using the small drift and the hammer, GENTLY tap this UPWARDS until it becomes loose then carefully lift it clear with the pliers and put it somewhere safe.
4. Using the 3mm drift and the hammer, tap out the sight axis pin from left to right through the body. Once the end of this pin has cleared the left sidewall of the rifle body press down gently on the rear of the sight with a finger just forward of the ‘battle sight’ at this stage you should be able to push the pin right through the body using the drift by hand. Once the pin is out of the rifle body, release the pressure on the sight and lift the sight out of the body. Under the sight on the right of the body is a spring and plunger which will be released under control as the sight is lifted clear. If a Mk3 sight is fitted there will be a small collar on the right side of the sight with the pin passing through it. This should remain with the Mk3 sight, it is not required with a Mk1, 2 or 4 sight.
5. Lift the spring and plunger clear of the body. Clean the rifle body of old grease and dirt. Check the plunger spring for damage or distortion and replace with the new one if required. Lightly oil or grease the spring and plunger and replace in the rifle body. The flat on the plunger goes to the right, flat against the rifle side wall. Check the cross pin. If it is damaged or worn (check for ‘grooving’ of the axis pin by running your nail down its length), replace it with a new one.
6. Place the new Mk1 sight into the body of the rifle in the folded down position. Push down on the back of the sight to compress the plunger and spring. Use the 3mm drift through the left side of the body to line up the axis holes, once lined up insert the new cross pin from right to left and push or tap it fully home with the hammer.
7. Axis pins may or may not have a screwdriver slot in the head. If the pin has one then using the screwdriver in the slot on the head of the axis pin, rotate the pin until the lock pin hole in the axis pin is lined up vertically with the slot in the left side of the rifle body. If it does not then ensure that the hole is vertical before pushing home. Carefully place the lock pin in place and, using the small drift and hammer, tap it into place. Note that this is a taper pin. It should be flush with the top edge of the receiver, do not drive it in too far or it may shear the end off of the axis pin!
8. Test the sight for full movement.