A photo of the sight in the barrel dove tail would really help. Actually seeing it may give us better ideas for a solution.
You may be OK.
Before the baby is thrown out with the bath water, take a real close look at what you have going on.
Sights are one of those things, that well....sometimes you may have to bludgeon them into submission with....a little bit of grace.
First lets refer to the sight it's self as the... "male".
The barrel slot the...."female".
By far the most common problem with lugs and sights I have encountered is this, The male tends to ride high in the female slot.
Reason... Most triangle files unless they are a specialized dove tail file, have a flat edge(about a mil or so). What happens here is at the base or the corners of the female slot, they are blunted. The corners of the male piece are sharp. The sharp corners of the male do not fit the blunt edges of the female slot. This causes the male piece to ride high as the sharp corners of the male piece will not fit the corners of the female slot.
Solution...
File the sharp edges of the male piece to fit the blunted corners of the female slot. It does not take much. Just a stroke or two.
A very easy mistake to make in fitting the male piece to the female slot is to open up the female slot when actually it's the corners of the male piece that's causing the problem. What you wind up with, is too big of a female slot....When the male corners finally fit...The whole female slot is too big.
You still have some adjustments here. If the male piece is copper or brass, you have a good bit of adjustment. Iron can be adjusted but for a big "adjustment" you may need heat.
Option # 1. Adjusting the soft copper/brass male sight base while it's in the female slot...
With a brass drift (you may want several I have 2 a really big one and a smaller one that I have ground for this an other purposes on a grinder. My small one is made from a hardware store brass rod maybe a little larger in diameter than a #2 pencil. I ground the round edges flat on one side...it looks a lot like a flathead screw driver but the "blade" is larger. This allows me to get next to the sight blade.)
With this drift I tap the top of the male sight base. If I'm real close, I can move enough brass or copper to better fill up the female slot. I tap next to the sight blade.....an all over the top of the male base.
This is one of those things that's pretty straight forward to do but incredibly hard to describe. You may....may have to hold your mouth just right while doing this.
So you have peened it(the male base) with a brass drift...it has filled the female slot pretty well but there's still some daylight.....
With that same brass drift you can work on the top "wings" of the female slot. Getting there....? Really close.
You can finish it off with a steel punch. Punch 4 maybe even 8 dots....2 to 4 on each side of the sight blade to lock it in the female slot.
Well you can see that this is not going to work...you have too far to go so....
Option # 2. Working the male sight base off of the rifle...
In a vise or with a vise hand vise combo go to work peening the base of the male piece... working on the top and the bottom. Expand it where it needs to be expanded. You can use a punch on the bottom side and even on the oblique sides that's covered by the "wings" of the female slot. What you are trying to do is displace metal to fill up the female slot.
Option 1....Option 2....Option 1...Option 2..... Back and fourth....back and fourth....Clean up the male piece with a file from time to time ....let the witness marks tell you where. Go slow be patient and maybe it will submit.
Option 3. Make a new sight base or whole new sight.(the Track oversize male sight base may work well here).
With a chunk of brass or copper....make a new male piece that fits the slot. The building books (the usual suspects) have instructions for making a sight. Jack Brooks on his page has a tutorial on making a barely corn sight out of sheet brass.
In my opinion....making an oversized male dovetail that actually fits the slot is a much cleaner and better option than trying to solder a teeny copper or brass shim into the female. It's a good theory but I do not know how well it would work out.
