Target Sight Adjustment

[rct269]

It is my recollection one full turn of a pre-war sight adjustment screw results in a change of the point of impact of 1" at 50 yards. True or False?

Similarly, it is my recollection a one "click" turn of a post-war sight adjustment screw results in a change of the point of impact of 1/4" at 50 yards. True or False?

Many thanks!

Ralph Tremaine

 

[Tom K]

I'll have to say "false" simply because the change in point of impact will depend on the barrel length. The change in impact due to one turn or one click for a 4" gun, will be less for an 8" gun. The exact amount will depend on the ratio of the distance between front and rear sights.

 

[HappyHunter]

I shoot bulleye.

When I use my 1947 K-38 with 6 inch barrel, I adjust 1/2 turn when shooting at the 25 yard line, after a 50 yard line zero. Using a 158 gr swc over a moderatly warm load of W231/HP-38.

This info is not what you asked for but relates somewhat.

 

[rct269]

Some of you may have noticed I posted this same question on the SWCA Members Forum. Roy Jinks responded to that one, noting a mid '60's instruction sheet provided this information. One click of elevation moves point of impact (approximately) 3/8" at 50 yards, and one click of windage moves it (also approximately) 1/4" at 50 yards. (I'm halfway to where I want to get.)

He notes this is from a Model 14 instruction sheet----K-38, right? He also notes there is no mention of any difference in the sights for J or N frames. It stands to reason (to me at least) that a manufacturer isn't going to make different sights for different frame sizes. They would certainly make different size sights to fit different size frames, but the internals figure to be the same. No matter really---this is close enough for government work.

A word or two about Tom K's response: He's right, the barrel length/sight radius certainly makes a difference----when you get right down to it. The factory apparently felt there were/are fairly few folks who want to do so. This is based on my observation that pre-war target sights are infinitely adjustable----and post war sights (an improvement??) are not. Go figure!

Ralph Tremaine

 

[DWalt]

If you have a good dial or digital caliper, you can measure the amount of rear sight movement for each turn or click (or at least get close), and if you measure the distance between the rear sight blade and the peak of the front sight (the sight radius), you can pretty easily calculate the change in point of impact at any distance per click or turn. Just use similar triangles.

 

[Hondo44]

Having shot my 22 Outdoorsman at the range last Sunday I adjusted the windage after replacing the rear sight leaf with the correct one. Approximately 1/2 turn of the screw moved the POI about 1". The threads are far coarser than the micro click sight.

And it's true, I have been forced on some S&W post war micro-click sights to adjust the rear sight between clicks for an exact zero.