How far does rear sight move?

Brianatc · Feb 8, 2014

This question came up the other day as far as how much adjustment was needed in a dovetail rear sight?

7" sight radius at 25 yards requires .09406" to move 12" on target.

20" sight radius at 100 yards requires .06704" to move 12" on target.

Wall · Feb 8, 2014

I just use the 1 tap, 2 tap, **** that's too far method

poopgiggle · Feb 8, 2014

Anyone with a pocket calculator who remembers trig from junior high can figure out how much to move the sight.

I still haven't figured out how to move a rear sight exactly .078" with a hammer and punch though.

Wall · Feb 8, 2014

poopgiggle said:
Anyone with a pocket calculator who remembers trig from junior high can figure out how much to move the sight.

I still haven't figured out how to move a rear sight exactly .078" with a hammer and punch though.

see my post above

mike cyrwus · Feb 8, 2014

how much dovetail movement needed depends on the relationship and precision of the guns bore at lockup to the parallelness of the sight cuts.
its a non issue really, if you consider that a typical rear sight is maybe .5" and youd want at least 2/3 of the sight in the dovetail for it to be secure, so you probably have .400" or more of travel if you assume that the dovetail is at least as wide as the sight is.

I think thats not what you were getting at, though. If so, can you expand?

mike cyrwus · Feb 8, 2014

to correct errors in POA/POI,
formula is

sight radius*error/distance from target= shift needed

works for elevation and windage

units must be the same.

If anyone is totally lost, then give me a call. Id be happy to have you help with my student loans Im paying on.

technetium-99m · Feb 8, 2014

poopgiggle said:
Anyone with a pocket calculator who remembers trig from junior high can figure out how much to move the sight.

I still haven't figured out how to move a rear sight exactly .078" with a hammer and punch though.

Drop the slide into a vise with flat jaws or inserts such that the sight is below the top of the vise. Measure with calipers from the sight to the surface of the jaw, will get you very close.

poopgiggle · Feb 8, 2014

technetium-99m said:
Drop the slide into a vise with flat jaws or inserts such that the sight is below the top of the vise. Measure with calipers from the sight to the surface of the jaw, will get you very close.

That's more or less how I centered the sights on the last set I installed. It just took forever tapping back and forth to get it right.

Brianatc · Feb 8, 2014

Like I said it came up in conversation with some one wanting to add a dovetail sight on a shotgun that was shooting slugs several feet off. They just questions if there would be enough adjustment, so I had a spare moment to figure it out.

technetium-99m · Feb 8, 2014

poopgiggle said:
That's more or less how I centered the sights on the last set I installed. It just took forever tapping back and forth to get it right.

If you lay the punch against your finger and brace said finger against the slide you can feel the punch move just slightly. Also, if you're using a framing hammer you are just making stuff difficult for yourself.

scubor2 · Feb 8, 2014

technetium-99m said:
If you lay the punch against your finger and brace said finger against the slide you can feel the punch move just slightly. Also, if you're using a framing hammer you are just making stuff difficult for yourself.

Burk says a framing hammer is too small.

Wall · Feb 8, 2014

technetium-99m said:
If you lay the punch against your finger and brace said finger against the slide you can feel the punch move just slightly. Also, if you're using a framing hammer you are just making stuff difficult for yourself.

Like I said

Wall said:
I just use the 1 tap, 2 tap, **** that's too far method

Bob Sanders · Feb 8, 2014

If it's an XDm, all you gotta do is get pissed off enough because everything is 6" left and pick up a short piece of something that may or may not be aluminum rod, borrow a cresent wrench from the range office, take the slide apart and wail the hell out of it. Problem fixed.

dennishoddy · Feb 8, 2014

poopgiggle said:
Anyone with a pocket calculator who remembers trig from junior high can figure out how much to move the sight.

I still haven't figured out how to move a rear sight exactly .078" with a hammer and punch though.

Set the gun up in a vise, and use a dial indicator.

mike cyrwus · Feb 9, 2014

Brian Lambert said:
Like I said it came up in conversation with some one wanting to add a dovetail sight on a shotgun that was shooting slugs several feet off. They just questions if there would be enough adjustment, so I had a spare moment to figure it out.

tell them the adjustment needed is probably in their finger