Sometimes I see old Marlins (or other guns) with extra dovetails or holes in the barrels. Often these holes or dovetails make the gun much cheaper, as most people pass up such guns because of the defects someone did to them. If the price is right I snatch them up quickly, as a little gunsmithing can make them very presentable!
Recent purchases I made in May in Denver at the Colorado Gun Collectors Show were two such guns. Both at huge discounts because of issues. One was a Schoyen Ballard schuetzen rifle with 6 extra holes, and two extra dovetails. The other a Ballard Rigby #6 1/2 schuetzen rifle, with one extra dovetail. The Schoyen was a big project, as it not only needed the holes filled, but a complete restoration of all the metal to restore it. But the Rigby Ballard only had an extra dovetail, and some trigger adjustments; and the rest was extremely nice! Did the trigger adjustment in seconds, but just got time to do the dovetail repair today. Here's the step by step.

I drifted out the rear sight blank, and got the Bronells 3/8" dovetail filler material out. Checked the fit to the dovetail, and it was pretty tight, so I figured it would be good as is. Cut a piece .75" long, and after gently tapping the edges of the barrel dovetail lightly, to ensure no gaps, I put red Loctite on the piece and drove it in place.
Next I taped around the filler with blue painters tape, adding numerous layers over the Rigby flats, just to be sure no accidents could harm them! Then I began filing the filler down with a coarse mill file. Once I got close to the barrel, I switched to a fine mill file. As I began to nick the blue tape, I switched to a very narrow fine mill file to keep my file strokes to just the filler. After getting the filler just barely high, I removed the tape and began blending it into the barrel surface. Once completely even, I got out my roll of 1" wide emery paper and stropped the filler and barrel to get the filler blended into the barrel contour.
I finished the fill with 320 grit emery paper sanding lengthwise to match the original barrel finish. Once it blended in well, I heated the barrel slightly with my heat gun, and hit it with Oxpho Blue solution. Then heated it again and hit it with browning solution to match the barrel's color. You can see the filler a bit about 2.5" in front of the Rigby flats.

The filler isn't invisible, but it's much better than an open dovetail, or a blank filler. You can't weld on a barrel without destroying the bore. The weld will move metal, which will create an irregularity in the bore. So cold filling them with a tight filler is the way to go. If a gun has a bad bore, then the filler can be welded in, and finished off. The barrel needs to be rust blued afterwards, as hot blue will show the different metallurgy, and expose the repair. Rust blue wont show the welded in filler, or different metallurgy.
When filling threaded holes, I buy soft steel rod and thread it with a die to the hole's thread size. I short thread the rod so it tightens before the rod bottoms out. Then I cut off the excess and peen the end down. After peening the end, I file them to fit the barrel contour and then polish them until they disappear. Then the barrels get the same tough up bluing, or a complete bluing if they need it.
Hope this makes you reconsider buying a project with holes or dovetails, as they can be bargains!
Recent purchases I made in May in Denver at the Colorado Gun Collectors Show were two such guns. Both at huge discounts because of issues. One was a Schoyen Ballard schuetzen rifle with 6 extra holes, and two extra dovetails. The other a Ballard Rigby #6 1/2 schuetzen rifle, with one extra dovetail. The Schoyen was a big project, as it not only needed the holes filled, but a complete restoration of all the metal to restore it. But the Rigby Ballard only had an extra dovetail, and some trigger adjustments; and the rest was extremely nice! Did the trigger adjustment in seconds, but just got time to do the dovetail repair today. Here's the step by step.


I drifted out the rear sight blank, and got the Bronells 3/8" dovetail filler material out. Checked the fit to the dovetail, and it was pretty tight, so I figured it would be good as is. Cut a piece .75" long, and after gently tapping the edges of the barrel dovetail lightly, to ensure no gaps, I put red Loctite on the piece and drove it in place.
Next I taped around the filler with blue painters tape, adding numerous layers over the Rigby flats, just to be sure no accidents could harm them! Then I began filing the filler down with a coarse mill file. Once I got close to the barrel, I switched to a fine mill file. As I began to nick the blue tape, I switched to a very narrow fine mill file to keep my file strokes to just the filler. After getting the filler just barely high, I removed the tape and began blending it into the barrel surface. Once completely even, I got out my roll of 1" wide emery paper and stropped the filler and barrel to get the filler blended into the barrel contour.
I finished the fill with 320 grit emery paper sanding lengthwise to match the original barrel finish. Once it blended in well, I heated the barrel slightly with my heat gun, and hit it with Oxpho Blue solution. Then heated it again and hit it with browning solution to match the barrel's color. You can see the filler a bit about 2.5" in front of the Rigby flats.


The filler isn't invisible, but it's much better than an open dovetail, or a blank filler. You can't weld on a barrel without destroying the bore. The weld will move metal, which will create an irregularity in the bore. So cold filling them with a tight filler is the way to go. If a gun has a bad bore, then the filler can be welded in, and finished off. The barrel needs to be rust blued afterwards, as hot blue will show the different metallurgy, and expose the repair. Rust blue wont show the welded in filler, or different metallurgy.
When filling threaded holes, I buy soft steel rod and thread it with a die to the hole's thread size. I short thread the rod so it tightens before the rod bottoms out. Then I cut off the excess and peen the end down. After peening the end, I file them to fit the barrel contour and then polish them until they disappear. Then the barrels get the same tough up bluing, or a complete bluing if they need it.
Hope this makes you reconsider buying a project with holes or dovetails, as they can be bargains!