Pretty typical that you may need to fit the locking lug on the magazine to the latch. Other than that, sometimes the mag sides are a little wide if your rifle has a tight mag well. Plastic mags will eventually break in, or you can sand the sides of the mag where they go into the mag well. I have a lot of AC-Unity mags in 7.62, 5.56 and 5.45. They are good range mags. Probably just need to file a bit of off the bottom of the locking lug on the mag.