First step is fitting the trigger. If you haven't yet, go to that page and read up on how to fit the trigger.
-Step 0.1, fitting the Standard Width Trigger
If you purchased the Full Width Trigger, you will already have done everything needed by fitting that trigger. If you have the Standard Width Trigger, you'll need to do this step.
The new torsion trigger return spring, which mounts on the trigger itself, will run into the trigger housing lip unless you relieve it. The trigger return spring fits in the groove machined on the left side of the trigger, as seen in the picture below.
If you don't relieve the lip on the inside of the trigger housing, that spring will run into the lip on the left side, bind, and cause your trigger to not reset. We use a small flat file to cut away about 1/3-1/2 of the lip on the LEFT side of the trigger housing, then cut off the bur, exactly like we do to fit the Full Width triggers. When finished, it should look something like this.
(It's easy to file on the wrong side of the trigger housing, so drop the trigger in more than once to check that you are filing on the correct lip)
-Step 1, Drilling the Trigger Housing
If you've got a Full Width Trigger, you are ready to start drilling. I'll be honest, this is the most stressful part of the entire project. It is BEST done with a drill press. You'll want to run a #21 drill past the trigger guard, and into the factory trigger return spring hole. That hole is drilled at an angle for exactly this reason, so the drill will slide right in. This is also why we are going through so much work to get rid of the factory, crooked, trigger return plunger. You can tape up the trigger guard to help protect it, as pictured, but honestly the drill bit will eat right through the tape as fast as anything. When we do it, we hold the trigger group as pictured and run it up onto the spinning drill bit. We run our index finger up against the bit, actually putting some pressure on the trigger housing to pry the trigger guard AWAY from the drill bit. That appears to be the safest way to go. In the picture below my index finger is lifted up for clarity, but normally it rides right on the trigger guard. My right hand is then used to hold the top/front of the trigger housing securely. When the drill pops through it has a tendency to pull up on the trigger housing and mar the guard, so you want to keep steady pressure on the housing AWAY from the drill bit.
Drill this hole all the way through.
While the drill bit is still spinning, pull the trigger guard off and drill a hole in the side of the housing as pictured. Location is not crucial on this one, as long as the drill bit is basically riding in that curve, you'll be just fine. Exactly square is also not crucial; get it as square as you can, but close enough really is close enough.
-Step 2, Tap the Holes
Using a 10-32 tap, thread both of the holes you just drilled. This is the easy part. You'll tap the rear hole from the back as pictured. These taps are designed to be self aligning, so you can basically shove it in the hole, aligned as you can, and start turning. It will catch and take care of the rest. Once you're in about half an inch, you'll want to turn the tap back 1/4 turn every 2-3 turns, to help break the chips and let them flow out of the hole rather than binding. Whether you are working on a polymer or aluminum housing, you don't need any tapping fluid. All the 10/22 trigger taps here in the shop have thousands of holes with no fluid. Run this tap in as far as it will go.
Pull the tap out and run the tap into the side-hole you drilled. You'll want to try and make sure the tap is as square as possible to the hole for this one, since it's so much more shallow. For the same reason, you also don't need to turn the tap back to break the chips; just run it in until you're past the taper on the tap, then back it out.
Step 3, Install the Set Screws
Your kit came with two set screws. One of these screws has a groove cut towards one end; this screw goes through the side hole, with the groove towards the inside of the trigger housing. This is referred to as the side set screw, or more accurately, the trigger return set screw. Obviously the threads on this screw have been removed at the tip to create the groove, so you'll want to back it into the hole. In other words, (if you're fingers are thin enough, not everyone here at Brimstone can do this without a tool) hold the set screw inside the trigger housing, put your hex wrench through the side hole, and run the set screw backwards into the hole until the grooved END of the screw (not the groove) is flush or below the inside surface of the trigger housing. In other words, so the screw is recessed enough that you can drop the trigger in. The other set screw is not grooved; it is the overtravel stop screw. Install this screw in the same way, run the hex wrench through the hole from the back, pick up the set screw, and back it into the hole. You'll want to run it back until it is also flush with the inside of the trigger guard, NOT like the picture where it is left extended for clarity.
Step 4, Install the Trigger
Put the new torsion trigger return spring on the trigger as shown in the picture below. It should sit down in the groove machined into the trigger. The shorter arm should sit against the trigger, and the longer end should extend up from the front of the trigger, and should be parallel or at a greater angle from the short arm. It should never be less than parallel. (This spring can also be made from a factory bolt hold open spring by clipping the dog-legged arm of that spring)
Slide the trigger assembly with the new trigger return spring, sear, disconnector, and disconnector spring installed into the trigger housing, the same as you would assemble a normal trigger. Install the trigger pivot pin.
Screw IN the side set screw (the trigger return set screw) until the groove is fully visible inside the trigger housing, but no further. We have a set of precision blade screwdriver with a tiny notch ground in the end to grab the long arm of the spring, and hook it into the groove in the side set screw. There is no need for Loctite on this screw, the spring tension will hold it in place.
Then check the underside of the trigger, looking through the trigger guard, and using your screw driver, pry the torsion spring AWAY from the trigger housing ensuring that it is seated fully against the trigger. Make sure that spring is away from the housing all the way around the trigger, looking through the top of the trigger housing as well.
Step 5, Adjusting Overtravel Stop
You're almost done, I promise! Assemble the rest of the trigger group as you normally would. With the hammer in the cocked position, screw in the overtravel stop until it just touches the trigger. Put a drop or two of Blue Loctite down the threaded hole onto the head of the overtravel screw. You can work it down the hole with the hex wrench as needed. If you try to pull the trigger right now, it shouldn't move at all since it's bottomed out against the overtravel stop. Your goal is to back that screw out enough to give your trigger the range of motion it needs to release the hammer, but no more. I usually back the screw out a couple of turns, then back it out in 1/4 turn increments checking the trigger pull every time. Eventually the hammer will release. Turn the screw ANOTHER 1/4 turn back AWAY from the trigger after the first time it releases, to be sure you have enough clearance for reliable function regardless of conditions.
And that's it, you're all done! It is a project for sure, and you should be comfortable working with tools and free-handing some stuff before you take on this project. If you have any questions or issues with this kit, direct them to Triggers@BrimstoneGunsmithing.com, and we will get you taken care of.
If you aren't fully comfortable with this project, be aware that the cost of a Tier 2 trigger job is the same as a Tier 3 + this trigger kit. It may be in your best interest to just buy a Tier 2 trigger job from us in the first place and call it good.
Hope that helps and again, if you have any questions just let us know!