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Should there be a gap under front sight when installed?

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Sidney Smith

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I filed in the dovetail for my front sight post today. I measured the thickness of the brass on the sight at around .055 inch, and the depth of the dovetail is just under that. I didn't want it to be too deep so erred on the side of caution. When installed there is a slight gap at the back of the sight where it does not touch the barrel. It's not excessive but its there. Is a slight gap in this manner ok, or should the sight be touching the barrel? At this point Im going to live with it, but was just curious.
 

Sidney Smith

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BTW, although expensive, the dovetailing file sold by Brownells is worth every penny. I'm glad I bought one. Works much better than making a homemade safe sided dovetail file from a common triangular file.
 

Stumpkiller

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Ideally: no. I have used brass shim stock to lower the dovetail in the slot to eliminate any gap. It is only a invitation to moisture, rust or crud to have a gap there.
 
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Sidney Smith

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I'm not concerned about crud or even rust as the barrel will be browned anyway. I'm more concerned it will show my novice building skills to easily.
 

EC121

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You might try putting some solder as filler on the sight base. Maybe the sight base wasn't flat when you installed it.
 

Scota@4570

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Don't be too critical of yourself. It looks best if you don't have any gaps. Sometimes stuff happens. IF the sight base is proud of the barrel you can pene it and clean it up after. On a round barrel I put a sight width flat on the barrel for the sight blade to rest on. I make every effort to have no gaps anywhere. A good set of digital calipers will make this kind of work more accurate. Worrying out dovetails with files is extremely difficult to get perfect. One thing that helps it to remove the sharp edge on the sight dovetail, they only get in the way. Use black sharpie marker to visualize where the parts rub. Don't use shims, it looks bad and is makeshift. Even with a milling machine I scrap about 1 in 5 sights. I make the sights myself to fit the dovetails I make. IF I botch the job I make a bigger sight. The small one goes in the parts box. Most are not as perfection oriented as I am.
 

Sidney Smith

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I may try tapping the sight slightly to see if it will reduce the gap. The gap is not excessive and would probably not be noticed by Any one (but me). I did file the bottom of the sight slightly as it had some kind of part number molded into it that was raised. I wanted to get the bottom as flat as I could. That might have caused The back end of the sight to not sit flat on the barrel.
 

rich pierce

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Sounds like the corner angles of the dovetail did not get filed level with the base of the dovetail. The safe edge file can be used tooth down, carefully, to level those corners with the base.

The other issue that arises is that it’s tough to file the sight base perfectly flat. I take a wide flat file and hold it in the vise. Color the sight base with a marker. Slide the sight on the file back and forth 10 swipes and inspect where the file is cutting. Re-color the base and repeat, after turning the sight base 90 degrees. When the file is removing all the color All the way to the edges, it’s pretty flat.
 

Larry (Omaha)

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Is a slight gap in this manner ok, or should the sight be touching the barrel?
A slight gap is not a huge issue, but will not be a correct install. (I know you want it correct, or you wouldn't have asked) The sight needs to be down home on the barrel. If your metal is still in the white, it is not too late to make it right. It isn't a mistake if ya can fix it.;)
Flintlocklar 🇺🇲
 

fleener

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Brass or aluminum from a beverage can works as a shim as well. The AL is nice and thin and wont rust.

Fleener
 

Vaino

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Have installed many rear and front sights w/ my "home made" dovetail file and started by breaking off the tapered front end of the file and grinding one safe side using the corner of the coarse bench grinding wheel.....this prevents over heating and yields a slightly hollow ground surface which lays flat on the bottom of the dovetail slot. Fully sharp corners are a must.

To start the dovetail, the bottom of the slot must be flat before filing the angles which are already there because a dovetail chisel was used to start and to raise a steel moldings for the rear sight and bbl lugs....the front sight raised steel is filed flush w/ the bbl. As was said, periodically the toothed surface of the file should be used on the bottom surfaces below the angled sides to insure that everything is flat and the inside corners are sharp.

I use a dovetail depth of .035 for the rear sight and all the bbl lugs and .045 for the front sight. The lower corners of all the parts have a small radius filed on to prevent any corner interference. The raised metal for the rear sight is filed into a molding and doubles the depth of the dovetail {.07}....the raised metal for the bbl lugs is peened down for a tight fit and then filed smooth. The front sight is filed in.

To see if the opposite sides of the dovetail are parallel and perpendicular to the bbl. 2 long, small dia pins are held against both sides ...the pins exaggerate any errors and the angled sides are then easily corrected.

Filing dovetails isn't all that difficult and is a skill that all gunbuilders should have......Fred
 
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