Only a couple notes here:
1. If you use a hack saw. Just take the time to square the cut up, use a chamfer hand tool and a chamfer stone and not a file to clean it up and create a proper crown. There are even crowning stones avail for a low cost. You can make a decent squaring jig with two pieces of tool steel and two bolts and a V cut in each square of steel, clamp it to the barrel * not too tight* and cut to the right side of the square with the barrel muzzle pointed to the right. I usually use a carbide hack saw, just makes for an easier start and a better cut.
note * cut the vent 1/8" longer than the barrel so you have enough to finish the vent end right if you cut the vent as a non post area. Just finish it back so the job looks pro.
2. DO NOT USE A PIPE CUTTER. It will swage the barrel where the rollers contact the barrel as well as roll the end piece in and you will in effect create an OVER FULL choke condition, if you shoot slugs, steel shot, flechettes and the like through it, the end could possibly fracture and become a mini grenade. I have seen it or I would not warn against it. Plus a pipe cutter is not practicle with a rib or vented rib.
3. Take the time to measure the ID to 3" inside, check the Brownells site for proper choke Vs. type of ammo and gauge, then spend the couple bucks for the shotgun bore hone and do the job right. When you hone, either use the hand hone with the stabilizer in the kit or use a decent drill press or mill/lathe so you do not create a wobbled honing job.
4. If you cut the vent where there is no post, use silver solder to reattach and seat the vent rib. You will have to make a short post piece for the end finish or ramp the Vent Down to the end of the barrel, file and stone, solder and polish, then finish with a good bluing agent. You of course would put the bead at the level part of the rib before the bend angel down. Also rem, you will have to adjust the height of the bead due to the shorter sight radius or you will pattern high or low, depending on how deep you set the bead.
There are even sight and bead install kits that make the job easy and look pro.
Brownells should have all the items needed for a safe and decent looking barrel cut.
http://www.brownells.com/aspx/NS/GunTech/links.aspx
Hope this helps
Happy Cutting
Mike