Cutting dovetail over chamber/bore...

SuperMag

I'm cutting a dovetail on a barrel for a rear sight over the bore, just ahead of the chamber of a .358 Winchester. The barrel is rather slender so this is a bit tricky. At the minimum, how much "meat" do I leave between the bottom of the dovetail and the bore?

MIKE WISKEY

you would be better off useing a screw on sight. your dovetail has to be the full depth of the sight (I'd guess .125"). take the barrel dia. at the sight and divide by 2 then subtract .358" and that will give you the wall thickness then subtract the depth of the dove tail=remaining barrel steel.

SuperMag

Yes, I know that already.

My question is --generally speaking-- how much steel, minimum, does there have to be between the bore of the rifle and the dovetail without having to worry about failure?

mpolans

I would think it would depend on the steel. Practically speaking, I can't think of how this could possibly be worth the risk. There has got to be an alternative method of mounting the rear sight that is safer.

MIKE WISKEY

I'D WANT A LITTLE OVER 1/2 THE THE DOVETAIL CUT OUT. IF YOU HAD A BARREL WALL THICKNESS OF .300" AND A DOVETAIL CUT OF .125" THIS WOULD LEAVE .175" OF STEEL UNDER THE BOTTLOM OF THE DOVETAIL. THERE IS NO STANDARD THAT I'M AWARE OF, THIS WOULD ALSO DEPEND ON THE CARTRIDGE (.358 WIN. HAS LOTS MORE PRESSURE THAN A .35 REM.).

Geri

Years ago when I was learning the trade, a riflesmith told me that a dovetail with a wedge (the sight) would put a stress on the barrel, and it would not shoot as well as if it were installed with screws, or with a barrel band. Just passing on what I have experianced.

mrbruce

Just exactly how thick is the barrel under the place where you intend to put the sight ?
Like MW said there is no standard for this, just commen sense.

SuperMag

As I figure it, there's 0.232" barrel wall thickness over that spot in the bore. There is currently a blind screw hole in that location that measures 0.150" deep.

I'm thinking that the barrel really doesn't need to be tremendously thick there; the chamber walls on my S&W .44 Magnum only measure 0.080", and the chamber wall thickness under the timing notches on that same gun mic out at 0.035"...

perry shooter

Hello Supermag one thing to consider The steel S&W uses in their cylinder is I suspect vastly different than Barrel steel used in your rifle. Just a thought.

SuperMag

Granted, and I have no intention of cutting the dovetail to within .035" of the bore.

But one thing can be said with certainty; the yield strength of the steel of each weapon has to withstand the proof load pressures of their respective calibers.

That said, the full depth of the dovetail of this particular sight is 0.090". If cut to full depth, this would leave 0.142" of steel between the bottom of the dovetail and the bore. Almost twice the thickness of the chamber walls of the .44. I'm thinking this would be OK...

bobski

i know this is only a 22, but i thought it might help to show that it can be done with regularity.
hope it helps.

mpolans

The .22 is not a reasonable comparison, what with the difference in pressures. Don't forget, it's not just the thickness of the barrel, but because you're machining edges into the barrel, you're talking about creating stressed areas in something that's already under a lot of pressure. I'd probably feel better moving the rear sight to the rear of the receiver or finding an expert to look in to brazing the rear sight on.

bobski

.22's create 40,000 psi chamber pressure. i showed this to help give an idea as to location of brass in relation to the dovetail, not only for the asking party, but for those watching and trying to invision the discussion.