It takes about 30 seconds..... Look on the underside of the trigger housing. You can see a small hole just in front of the trigger guard. Inside the hole you can see a spring and endcap. Use a pointed object to push the cap toward the rear. The mag catch will pop out. To replace the catch, push the spring cap back in from the front and hold it while you slide the new mag catch into place. Once the catch is half way across the cap hole in the front of the housing, you can remove whatever you are using to depress the spring and push the catch the rest of the way in. It takes much longer to tell you how to do it than it does to actually do it. Someone around here probably has a spare M2 catch that they would let you have cheap. Just ask.