This is how you can have a semi-automatic gun turn into a automatic gun.

First, get a gun that is semi-automatic.

Then, hit Y and X and the same time. Note: This may cause a malfunction with the controller.

After that hit LT & RT simultaneously for 10 seconds.

Then tap A and it should work.

Note: This was tested with the M16, M14, FN FAL, and Olympia. All were successful except the M16.