I had a tool from Brownells that you chucked up in drill press
after you drilled hole. It was a tap holder with bearings that
lined up perfect with hole and kept it straight. It was turned
by hand with T handle. I never had much trouble with #6x48
taps, except in some hard 98 actions. The ones I had trouble
with were #3x56 and #45 bit for shotgun beads. Shotgun
barrels are not hard. You have to drill very slow to allow the
ribbon to clear bit flutes. If you don't bit will sieze and snap off.
You must have a decent drill press, if it has any wobble play
it will snap bit when it touches surface. And tap must be run
softly, it doesn't take much to twist off a #3x56 tap. I hated to
have to work on guns guys tried to drill with hand drill. I can't
do it or would I try, even on a cheap gun.The Forrester sight
drilling jig is also a handy tool but pricy. Like some already said
precision measure and layout should be achieved before you
turn on the drill and a good machine vice is a must.