If your barrel has the large front blade it is brazed on during assembly. There will be no threaded hole from factory. You will have to remove or lower the front sight and drill and tap for a bead. Also if it is the removable choke model you will have very little material left to hold the bead if you completely remove the sight. The short barrels usually shoot high with just a bead so your best bet would be to pattern the gun, find out how high your front bead needs to be, grind the original blade down and use it as a raised base to drill, tap, and install a bead at appropriate height.