This is a complete explanation of the trigger adjustments and how each one effects the mechanism...
Before we dive into specifics, let’s spend some time defining the terms used to describe triggers and trigger pull. A good trigger pull has often been described as akin to breaking a glass rod – the rod will not move when bent until it breaks. Just like the glass rod, a good trigger will not move perceptibly until the firing pin falls. We call movement before the trigger breaks “creep.” A creepy trigger then, is one that has perceptible movement before the sear breaks. The “weight of pull” or simply “weight,” is the amount of pressure required to break the trigger. Finally, the term “backlash” is meant to describe how much the trigger moves after the sear falls.
Speaking of the sear, exactly how does a trigger work? As you might have guessed, that is a function of the trigger design. In the case of a bolt action, the trigger serves to release the firing pin housed in the bolt. The surfaces that control the release of the firing pin are called the trigger sear. On a Winchester Model 70 trigger, the trigger itself engages the firing pin. This makes for a simple trigger, but this design has drawbacks. It is difficult to obtain a light trigger pull that is creep-free – there is too much friction. The Remington trigger, which first came out in 1948, uses a lever between the firing pin and trigger to eliminate the friction problem. Figure 1 illustrates the basic design of this trigger, which has been copied by many other suppliers. A Timney trigger, for example, is almost an exact replica of the Remington (but of higher quality). Essentially, the middle lever contains a square edge that bears against another square edge that is part of the curved trigger. When a shooter pulls on the trigger, it causes the square edge to move forward, which in turn causes the opposing square edge on the middle lever to become unsupported. Because the opposite side of the middle lever has an angled surface that bears against another angled surface on the firing pin, the lack of support of the middle lever causes it to fall and the firing pin to move forward.
The pressure required to break a Remington trigger is a function of the weight of pull and the trigger sear engagement, or the amount of engagement between the two square surfaces. If you look carefully at Photograph #1, you can see the two surfaces (look at the hole in the trigger housing just below the receiver cut for the bolt handle). Both the sear engagement and the weight of pull can be adjusted, as can the amount the trigger moves after the trigger release, also called backlash. Photograph #2 shows the front of the trigger housing; the two screws in the photo are used to adjust the weight of pull and the amount of backlash. Photograph #3 shows the backside of the trigger housing, which contains one screw used to adjust the sear engagement.
Of course, the first step in adjusting the trigger is to remove the barreled action. On actions that have a floorplate, this is accomplished by removing the two screws on the trigger; on the ADL model there is a trigger guard retaining screw that must also be removed. Following removal of the screws, simply pull the action out of the stock. On an ADL model, you must remove a magazine box retaining screw; on the BDL version, this can simply be pulled away. If you examine the trigger housing, you will see that the screws on the trigger housing are covered with a shellac-looking substance that prevents movement of the adjustment screws. This substance must be removed before adjusting the trigger screws; a sharp knife or razor blade is best for this. The back screw, the sear adjustment screw, is the most difficult to clean, but if you don’t do this, you will ding up the screw head. Now let’s discuss exactly how to adjust the trigger.
The first screw I adjust is the weight of pull screw. Cock the trigger by lifting and closing the bolt. Backing the screw out will lighten the trigger pull, because it elongates the return spring. Back out the screw and test the pull either by feel or with a trigger pull gauge until it feels right. If you cannot cock the rifle, it means you have backed the adjustment screw out too far - screw it back in until you can cock the rifle. The sear adjustment screw, the one on the back of the trigger housing, also controls the trigger pull – specifically, it is used to control creep, or trigger movement before sear release. However, it also contributes to the weight of pull, because it controls the bearing surface between the middle lever and the trigger (in other words, it controls the how much metal to metal contact there is). Screwing in the sear engagement screw reduces the amount of creep, or the amount of trigger travel before breaking the sear. Moving the sear engagement screw in too far will result in an inability to cock the rifle (I usually play with both the weight of pull screw and sear engagement screw to achieve the desired trigger pull). One criticism I have of the Remington trigger is the amount of goop they put on the sear engagement screw – I have dinged up several trying to turn them.
The next step in adjusting a trigger is the most important – ensuring safety. I run through several tests, the most basic of which is cocking the action by lifting and closing the bolt. If the action does not stay cocked when cocking the action very quickly, the trigger pull is too light. If the action passes this test, I then lift the bolt, pull it back to the rear, and slam it forward as fast and forcefully as possible. If the gun stays cocked after several iterations of this step, you are almost home free. The next step is to cock the rifle, grab it by the barrel, and slam the gun against the floor. If the sear releases, the trigger pull is too light. Finally, if it passes all of these tests, cock the rifle and put the safety on “safe.” Now lightly touch the trigger and push the safety forward. If the sear releases, it is time to go back to the drawing board.
After establishing a safe trigger pull, backlash adjustment is next on the agenda. This step is simple – cock the rifle, then screw the backlash adjustment screw all the way in. Now, with the screwdriver in one hand engaged in the backlash screw, pull the trigger with the other hand. The rifle will not release the trigger, but keep pressing on it and slowly back out the backlash adjustment screw until the sear falls. Cock the rifle and press the trigger a few times to ensure the firing pin falls. You are now finished adjusting the trigger. The last step is to cement the screws with any agent that will freeze the screws in place so they don’t move. I use fingernail polish; anything that can later be removed will work.
