Half circle rear sight

[seamaster]

Just fooling around, shooting with the circular rear sight I made long time ago.
Surprisingly easy to shoot. Grouping was very good.
Easy and good group, what else do I want?
Thinking about making it de facto rear sight.

Anyone use those circular rear sight as your de facto rear sight?
For those who used it, liked it, but switched back. Why?

[Rover]

Are you referring to the "half moon" notch popular with the Russians some years back?

[jetpoweredchicken]

I use the half moon sights on my TOZ-35 free pistol The rear sight blades included with the gun has square notch on one side and half moon shaped notch on the other (flipped over).

With a rectangular notch, the gaps increase in the x dimension only resulting in more light on one side and less light on the other. But with the half moon shaped notch, the gaps increase and decrease in both the x and the y dimension. This significantly increases the balance of light and consequently the shooter's sensitivity to a change in sight alignment.

[seamaster]

It is purported that half moon notch was easier to make than the precise edged rectangular notch by the Soviets.

Easier to make, easier to align.

I assume the scores would be the same either way with half moon or rectangular notch. Nygord set his US free pistol record with half moon.

Could you make a case to use half moon notch as a center hold? Like s “half peep” center air rifle sight?

[seamaster]

As to X and Y movement, I can see it is easier to pick up X movement with half moon notch, but I don’t see how it would help you on the Y axis movement though.

[seamaster]

Just got me really thinking here.

To pick up Y movement on a circular notch, circle is best cut not half way, but cut across probably 1/4 down from above.

That would give you easy pick up on X movement, and with those two “horns” on top of either side, that would give you easy pick up on top front sight Y movement.

I would assume that would be hard to make with metal rear sight, but very easily made with 3-D printer now a day.

Is it legal according to ISSF rules? Or does it have to be strictly straight rectangle rear sight?

[Rover]

I don't think the rules say anything about notch shape.

I have owned pistols with too narrow rear notches, so I just take a 3/16" chain saw file and open them up. The files are cheap and have no taper.

On several guns with interchangeable rear sight blades, I would usually take the smallest one from the spares because it was the most useless.

Angle the file to the outside of the bore line so that you don't "see" the side of the cut.

I much prefer the half moon because you can see misalignment much better, but some sights don't easily lend themselves to this treatment.

[william]

"I have owned pistols with too narrow rear notches, so I just take a 3/16" chain saw file...."

Rog, just don't try it after you've had a couple. You may forget a word and take a chain saw to your sight.

[Rover]

Always trying to spoil things. It's WAY more fun using a chain saw, especially on a Steyr.

[stephen_maly]

I think if it were I, it would be a small countersink in conjunction with a drill press or milling machine. Using a chainsaw file would work, but the user should practice a few dry runs first. I agree with Rover (whom ever he is) that the smallest notch is the least useful. Of course, the smallest-notched rear sight may have been made with enlargement in mind anyway.