how to measure a dovetail for the right sight

[texasranger]

picked up a rifle minus the front sight, thought I measured right and ordered a sight twice each time coming back not fitting. I am doing something wrong just not sure what. Help, what is the correct way to measure for a dovetail sight?

[DandJofAZ]

Tried that ...used file on sight...now fits fine

Doug

[mongrel]

It might be easier to say what kind of rifle it is.

If it's a CVA, Traditions, or one of the other foriegn-made types, the dovetails should be 10mm. This is a hair smaller than 3/8" -- .360" as opposed to .375".

Some of the Investarms (Italian-made) rifles might have 3/8" dovetails, but all I've dealt with have 10mm.

American-made guns and a few of the foriegn ones will have 3/8" dovetails.

If the problem is the sight base being too large for the dovetail, take a small triangular file and grind the teeth off one flat. Either enlarge the dovetail in the barrel or reduce the base of the sight. The "safe" (toothless) flat of the file goes in the bottom of the dovetail or along the bottom edge of the sight, depending on whether you intend to modify the dovetail or the sight base.

I would modify the sight base -- sights are a whole lot cheaper than barrels if something goes wrong.

In the meantime, let us know what kind of gun it is and a definite size can probably be established. The difference between 10mm and 3/8" is so slight that most measuring methods might not show it.

[flintboomer]

Part of the question is whether the dovetail is too tight or too loose. If a 3/8 sight is too loose then the dovetail is enlarged and may be why the front sight was missing. If so you may be able to peen or stake (center punch) one of the sights you have in place if it is not too drastically enlarged.

[texasranger]

The rifle is a custom one. I was told the barrel is a green river but I can't find any marks on it. I measure front to back of the dove tail one half inch side to side 7/16" and 1/8" deep. Help

[Dogshirt]

Sights are meant to go in from one side only, hence the side to side differance. I go right to left, but that's just me.
I should add that's as if you were shooting, right to left.

[Blackfeet]

Sights are meant to go in from one side only, hence the side to side differance. I go right to left, but that's just me.
I should add that's as if you were shooting, right to left.

Not sure that I understand this one, are you saying that the dovetail is biased to one side..............? I suspect that the dovetail is just a dovetail as it would be somewhat difficult to intentionally machine a slot off to one  side?

[Dogshirt]

That is what I'm told. In from the right out to the left.

[flintboomer]

Dogshirt is correct concerning hand filed sights on older rifles.

That sounds like a handmade sight was originally on the rifle. You may need to have a new slot cut and a spacer put into the old slot if you can't find one with a 1/2 inch base.

[texasranger]

Thanks for the help boys. I will let you all know what I come up with.

[mongrel]

FWIW, I file my dovetails the same width from one side to the other -- and don't recall ever, in any gunsmithing how-to books or articles, reading that I ought to be doing it otherwise. In fairness, though, I've run across several barrels with very definitely tapered front sight dovetails. These were all factory-done, I think all T/C, but it's been awhile since encountering one and I'm lucky if I remember for a certainty what I had for supper two nights ago.

This sight might solve the problem: http://www.trackofthewolf.com/Categories/PartDetail.aspx/874/5/FS-PA-39-B

Though the dovetail on this sight (also available in steel, BTW) isn't quite a full 1/2", a thin brass shim soldered to the underside of the base will not only thicken the base but extend its length. I'd try the sight as-is before going to the trouble of soldering, in case the dovetail is a hair under 1/2", and if it's a fairly snug but not QUITE snug enough fit, pein the edges of the dovetail slot to crimp the sight in place.

[texasranger]

Thanks Mongrel, that sight looks good. I will give it a go and let you know what happens. thanks