LIAI 7. 62 RIFLE SERVICE / MODIFICATIONS
by Terry Walsh, FSG

Failure to Function

The L1A1 was designed to function satisfactorily on a minimum gas regulator setting #4. This was to ensure an adequate reserve of gas for the user.

The following list of possible failures should be investigated and corrected by normal cleaning, adjustment, lubrication or replacement of unserviceable parts before proceeding with the modifications.

1. Cleanliness – all aspects
2. Lubrication – all aspects
3. Distortion of any component/assembly which may produce friction
4. Burrs – especially in chamber at extractor way, which may give hard extraction
5. Bulged or worn chamber
6. Contours of hammer and breech block carrier
7. Lack of hammer overdraw
8. Worn gas regulator, weak retaining spring gas regulator, pin fixing gas cylinder missing, gas cylinder loose distorted or dented.
9. Gas plug worn, gas piston worn or distorted, spring gas piston worn or distorted.
10. Return spring distorted.
11. Distortion of or misalignment of return spring tube.

Refitting Gas Cylinder

The objective is to close fit the cylinder so that the slots gas cylinder are aligned when the gas cylinder is screwed seated, thereby directing maximum gas flow to the gas piston.

Remove hand guards, spring gas regulator and gas regulator, tap out pin fixing gas cylinder with a 1mm parallel punch. Note position of gas cylinder gas slots with cylinder screwed seated. Unscrew gas cylinder and screw retain handle.

Machine cylinder head leaving a bevel on the inside leading edge to allow free movement of piston.

File the bottom of gas slots in a radius to prevent cracks propagating and allow for material removed from cylinder head.

Refit cylinder, screw seated, check for correct alignment of gas slots, remachine cylinder head if necessary until gas slots gas cylinder are aligned when the gas cylinder comes to rest.

Remove cylinder, wrap threads with thread tape.

Refit cylinder and screw handle retain, align slot pin fixing gas cylinder, use loctite #262 when refitting pin fixing gas cylinder. There should not be rotational movement of the gas cylinder.

Range test for functioning. Standard required – rifle is to function on minimum gas regulator setting #5, minimum ejection distance 3 metres, with factory standard ammunition.

If rifle fails, proceed to stage 2 repair.

Reaming Barrel Gas Port

Four reamers are required – 2.6mm, 2.7mm, 2.8mm, 2.9mm. Barrel gas port is 2.5mm.

Ream barrel gas port using 2.6mm and 2.7mm reamers. The bore should be protected from damage by inserting a 6mm diameter steel rod 500mm long in the bore. Remove any burrs with a tight fitting bore brush on a cleaning rod. Pass a .297 bore gauge to ensure the bore is clear.

Range test for functioning on minimum gas regulator setting #5.

If the rifle fails, ream barrel gas port using 2.8 and 2.9mm reamers.

Any rifle which still fails after stage 2 should be fitted with a new barrel.