Trigger
1. The zero trigger is one of the best upgrades you can get. However it comes at a price. It does not have a safety. It also requires a tiny bit of modification to the trigger guard. Cut as shown on the back of the package. It should look similar to this. Keep setting it on the rifle with the trigger loosely sitting on it to check for fitment.
2. Do not do this unless you are having lots of problems and they aren't solved by my problem solving advice to come later. I had to file down my receiver to ensure good sear catching on the piston. If you own a copy of the tm rifle you might have to do this more so then with the normal tm. I know what I was doing before attempting this and what to look for.
3.To install the new trigger you must remove the small brass block at the back of the zero trigger. Screw this to the gun first then attach the trigger to it.
4.Screw the rest of the screws in. Now you must pull down on the the rod that has a hole in it within the trigger system this will make it drop down so the bolt can be slid in. Slide the bolt in and push that pin back up. Attach the trigger guard should look something like this.
Now just follow the reverse of my steps with the stock and your good to go. or continue on for barrel hopup and silencer.