Ok, here's the deal. I have a 16" N4 barrel with the Swithcblock installed. I am going to send it to ADCO to have it cut down to 12.5 inches. I will then be installing an M4-2000 suppressor on it, which will stay in place most of the time.

1. Does anyone here have one that has been cut down?

2. Does anyone know what the proper gas port size needs to be?

3. Any known issues with it afterwards?