No, I do not recommend trying to do this on a real gun.
No, I am not going to be held responsible if you bring this into a public place and are shot for flaunting a weapon (Or so the cops thought).
Step 1: Gather the materials
~BIC pen (Tube)
~Aviator snips or scissors
~Hot Glue Gun
~Hot Glue Sticks
~PVC Pipe (Any diameter you want)
~Airsoft BB's (Optional)
~Airsoft Gun Lube (Optional)
Step 2: Getting Started
1. Start by taking the BIC pen and removing the end cap and internals.
2. Try to fit the pen tube into the end of your gun, if it fits - see step 4, if not then see step 3.
3. Next, take the aviator snips and clip 4 triangles into the bottom of the pen tube. This will allow some flexibility in the shape of the tube, so that it can be squeezed into a tighter hole.
4. Test by shoving into airsoft gun barrel (Should not go into the brass inner barrel)
5. If it does not fit, continue to shave a little bit more off the triangular cuts each time until it fits.
Step 3: Adding the outer silencer
7. Mark with the sharpie the desired length of your silencer (Roughly the same length of the BIC pen tube).
8. Use a saw to cut the PVC pipe to the desired length.
9. Use the flat file and sandpaper to make the PVC pipe nice and even and smooth.