The above reason why NOT to cut the barrel down are very valid.
With that said, here's the mechanics on how to do an easy home cut-down job:
First, drop a cleaning rod, dowel rod, or thin tape measure down the barrel, while it's ON THE GUN.
Mark the rod or measure at the muzzle.
Measuring the rod to the mark gives you the "official" barrel length.
Measure off 20 1/4" from the end. This is going to be the new barrel length. (Always give yourself 1/4" for final sizing).
Remove the barrel and lay the rod along side the barrel, with the original mark aligned with the muzzle.
Mark the barrel at the 20 1/4" mark.
MEASURE A FEW MORE TIMES, to INSURE you have the ACTUAL original barrel length, and the new barrel length properly ID'd.
Wrap a piece of tape around the barrel at the mark where you want to cut, keeping the tape as square with the barrel as possible.
PAY ATTENTION. Don't forget WHICH side of the tape the actual cut will be. People have gotten careless and cut barrels TOO SHORT by cutting on the wrong side.
Get a GOOD, high-tension hacksaw, with a fine-tooth blade.
Start by making a small one or two stroke cut, just enough to break through the finish to bright steel.
Rotate the barrel, and repeat the shallow cut, continuing to make cuts and rotate the barrel until there is a line all the way around the barrel.
Then just keep making small two or three stroke cuts and rotating the barrel until the barrel is cut through.
This method keeps the cut square with the bore, and prevents having to do a lot of filing to try to square up the muzzle.
After the barrel is cut off, use a fine-cut file to lightly smooth the cut end of saw marks.
Use the file to lightly break the sharp outer edges of the muzzle.
Put some fine sanding cloth over your thumb, and use this to break the sharp inner edge of the cut.
Touch up the bare end of the muzzle with cold blue.
To replace the bead, buy a Remington-type front bead from Brownell's Gunsmith Supply
http://www.brownells.com
This is a duplicate of the bead-on-a-base that Remington puts on it's Police guns.
Epoxy MIGHT hold it in place, if you get a good bond, but you're better off soft soldering it on.
Colonial Arms Shotgun front sight and base..#198-104-101
$7.50.
There are other methods of cutting shotgun barrels, one of which uses a tubing cutter to mark the barrel, instead of using tape.
The real keys are:
MEASURE PROPERLY. Cut too short, and you can't put it back.
Make short, shallow cuts, moving around the barrel until it's cut through. This keeps the cut square.
It's not absolutely necessary to replace the bead. Some people shoot quite well with no bead, and some people paint a short, wide white line down the barrel near the muzzle.
This seems to work well for some people in bad light.
