how thin is to thin

[oldgunguy]

I am working on a couple swivel breech barrels for my next SB rifle. My barrels are very thin and tapered, were I want to put a rear sight is about .768 dia. the bore is .45 cal with I think about .010 deep. I have very little wall thickness, my dovetail is about .040 that's about as deep as I think I should go. I don't want two places for the ball to leave the barrel. Any ideas....the front sight I will solder on.

Thanks, Bernie oldgunguy
 

[L. Akers]

.040 is more than deep enough.  On very thin barrels I will cut the basic notch about .032 then use a cold chisel to raise the dovetail angles.  I don't have to make a deep cut in the barrel but the sight is held in a full dovetail.

[mark esterly]

with your numbers my math gets .109 wall thickness left at the dovetail (if i'm correct which ain't often).  you get something different?

[Mark Elliott]

Don Getz once told me that the rule of thumb is a minimum .100" barrel wall thickness between the bottom of the dovetail slot and the bottom of the rifling.  My math gives you .109" of barrel wall thickness with a .040" deep dovetail.   I think you are good to go, but I would make the dovetail as shallow as you can.

[jerrywh]

  There is almost no possibility of a dove tail blowing out even with a thickness of .050.  The surrounding metal supports it a lot and there is very little pressure on a spot that small.  The real expert on this stuff is Davec2.  Besides the bullet is already moving up the barrel at that point and the pressure decreases as the bullet moves up the barrel. I have proofed a barrel that had a wall thickness of .032" at a distance of 10 " from the breech with 150 grains of ffg and two 54 cal. patched balls with no negative effects. That barrel was fired three times with that load. The barrel was made of annealed 1137.

[kutter]

Make the rear sight two pieces. A base and a transverse blade in a dovetail in the base. The latter will still afford windage adjustment.
Solder the base to the bbl. That avoids any dovetail cut in the bbl itself.

It can all be made up to rather small graceful  dimensions. Doesn't have to be a large clumsey looking thing.

[oldgunguy]

Thanks guys for your time and info. Hope all is well with our USA and thanks to all our military for keeping us safe.

Bernie/oldgunguy