It takes three hands to get the long spring back in, but its easy to do. get a coat hanger, a heavy wire one, cut the hanger on the bottom and slide the spring on to the hanger, stick the end of the hang that you just cut into the hole in the receiver, now using a small screw driver or ignition wrench, press on the end of the spring and let the spring be guided by the coat hanger. When you get the spring all the way in, carefully remove the coat hanger, replace the spring follower in its place and then drop in the trigger group.