The front sight is brazed on.
You can't just knock it off.
There are two ways to get it off and at least one way to use it for the bead.
1. Heat the barrel to a red heat until the braze melts, then bump it off with a gentle bump of a small hammer.
Note that the braze used melts at or above 1100 degrees.
Also note that the red heat will ruin the barrel's finish so it'll need to be refinished, and you'll probably want to re-polish the inside of the barrel with some 0000 steel wool on an old shotgun brush on a cleaning rod run in a drill.
2. Cut the sight off.
Start out with a CAREFULLY operated hacksaw to cut off as much as you can without any chance of cutting into the barrel.
Once you have most of it off, you can use a carefully operated bench grinder to take more off, then switch to files to get the remainder.
If you're careful, all that's left is a bare spot on the barrel that will need to have some kind of finish work done.
3. Carefully cut and file the sight down until just a low base is left. Drill and tap that for the bead.
Remington uses a brazed-on base pedestal for factory bead sights on non-vent rib barrels.
This gives a good strong mount for the bead, there's no problems with having to drill the hole into the bore, and theres only the bare metal of the filed down sight/base to be finished. For that, a coat of paint works well on the small area.
This usually works out better than totally removing the base, unless you're going to have the entire barrel refinished.
