These instructions are similar to others found on the internet, but with an important difference. I have a far easier method of installing the rear sear's return spring, noted in the last section on this page.
Part numbers in article refer to this picture:
To aid in visualizing the components:
Adjusting the Trigger
The following adjustments are possible:
• First stage travel
• First and second stage pressure
• Second stage movement (also called creep)
First Stage Travel
Adjustment of the first stage travel is achieved by removing the action from the stock and moving the down-stand on the front underside of the trigger unit.
To reduce first stage travel, the down-stand must be bent towards the rear of the trigger unit by tapping with a hammer and drift tool. Remember that this will reduce the setting position and sear engagement, so don’t reduce it too much. Moving the down-stand forward will increase sear engagement and first stage travel. Down-stand arrowed below:
First & Second Stage Trigger Pressure
This is the pressure required to pull the trigger through both the first & second stages. Both are affected because only one spring is used (part 51c), and the difference between first and second stage pressure is achieved by the difference in effective leverage between the front and rear rollers crimped into the top of the trigger blade, relative to pivot pin of the tongue/guide (parts 52a/52).
Turn the rear trigger adjustment screw (part 51a) clockwise to increase the trigger pressure, or anticlockwise to reduce it. If you reduce the trigger pressure too much, the trigger blade will not return if you release pressure on it during first stage travel. Also the second stage pressure can be too light making it unpredictable and dangerous.
Some second stage trigger movement is essential otherwise the trigger will fire the rifle at an unpredictable position during its first stage travel.
To adjust the creep you have to remove the trigger guard in order to access to the front trigger adjusting screw (part 52b).
In order to safely cock the rifle to test the set-up, the action has to be fixed to the stock without the trigger guard in place. One can make a spacer so that the stock can be fixed to the action with the rear trigger guard bolt sans trigger guard.
To adjust the trigger creep, use a Torx TX8 tool to turn the front trigger adjusting screw (part 52b). Turning the screw clockwise will reduce creep, and anticlockwise will increase it. If the screw is turned too far clockwise, then the trigger will have no second stage pressure and it will release unpredictably during the first stage travel. This is very dangerous, and if this occurs, then the front trigger adjusting screw must be turned anticlockwise at least half a turn, or until the trigger is safe again.
Dismantling the Trigger Components
Remove the whole trigger unit from the trigger block by drifting out the two retaining pins, taking care to capture the safety catch and spring when pulling the trigger unit from the block. Also take care not to lose the small hexagonal nut that sits in the rear of the trigger housing for the rear trigger guard screw on most models. You can avoid losing this in future by using some insulating tape around the back of the housing to make it captive.
Remove the rear trigger adjusting screw and spring
Remove the trigger pivot pin and the trigger
Drift out the pivot pin for the guide and tongue, and remove parts 52 & 52a. The trigger unit now has only the piston sear & the upper sear lock rotated out by their springs.
Tap out the retaining roller part 50f, and remove parts 50d & 50h (carefully noting which way the spring goes for re-assembly).
When viewed from the back of the trigger unit, the rear sear spring (part 50i) is on the left and the spacer is on the right. If you look carefully inside the trigger housing, you will see that the rear sear spring is kept tensioned by a pin roughly in the middle of the trigger housing. The rear sear is kept from rotating all the way around thus releaving it's spring pressure by being caught by the width of the Piston Sear Lever's return spring. Insert a wedging tool and separate the two sides of the trigger housing enough to allow the rear sear to pivot past this spring wire. The rear sear will now have no spring pressure on it.
Now tap out the pin holding the rear sear, and thus remove the rear sear, spring and spacer.
Reverse of dismantling. Some instructions on the internet make the rear sear assembly challenging, using a homemade tool to push the spring wire up into position. It is always much easier to use the part itself that is tensioned by a spring to rotate the spring. Do so in this case in the reverse of the disassembly method. I.e., install the rear sear upside down with it's long wire end over the pin it rests on. Insert the pin the sear rotates on. Rotate the rear sear thus tensioning the spring. When you run into the thicker spring wire for the Piston Sear Lever's tensioner, wedge the sides of the trigger assembly apart enough to squeek the rear sear past it. Once rotated into postion, insert an allen wrench through the hole that will keep it in the rotated position while you install the lower trigger group parts.