You are getting good info.
If you divide the sight radius into the range you are shooting you will get a number that is the multiplier of any sight adjustment you make.Of course,you must convert to the same units..I'll give you an example(I do not have my calculator handy,so I'll use simple numbers)
Suppose you have an 18 in sight radius.We can call that 0.5 yd.If you are shooting at 50 yds,0.5 yds goes into 50 100 times.So,with these numbers,if you need to move the group 5 in at 50 yds,it would be 0.050 at the sight.
I'm telling you this so you can have an idea how much to move it.The brass punch and tapping hammer are correct.Of course,you do the tapping on the dovetail part of the sight,not the leaf spring the sight blade is on.
Before you start whacking,however,I would consider this.Those dog leg stock older guns with lower velocity rounds are a bit "dynamic" when fired.Recoil is starting before the bullet leaves the barrel.
So,as has been suggested,a benchrest group point of impact may not be the same as the sort of shot you might typically take with a 30-30.
You migfht,for fun,see how it shoots standing on your hind legs at 50 yds.Shoot 10 real careful and find the center of the group.See if it is still off that much.
Its not real easy to get a good spot weld on that rifle on a bench.You are also dealing with a slow lock time,and open vs peep sights.Try sight black on your gold bead,focus on the front sight but really concentrate on a perfect sight picture as you squeeze,then follow through and call the shots.
If the barrel is in good shape,that old 30-30 will likely give "minute of battle rifle" 3 inch groups or so at 100 yds. IMO,they are about a 150 yd rifle.
Be a little patient.Its not an M-4.Have fun!