20 October 2015

Complaining Just To Complain

I shoot the Finn mosin's better than Soviet.

I've talked to someone who's the opposite.  He opined that the Finn front sight is too wide for fine work...

This got me curious, so out come the measuring tools!

Finn Kiv/28-30.  Front sight is 0.102" wide.  Rear notch is rectangular 0.073" wide and 0.041" deep.

Soviet M91/30.  Front sight is 0.087" wide.  Rear sight notch is a half circle ø0.067".

Finn Kiv/39.  Front sight is 0.095" wide.  Half circle rear sight notch ø0.085".

Distance from my eye to the rear of a 91/30 is 13-15/16".  The rear sight on the Finnish guns is 0.475" closer to the eye.

Distances between the sights are, Kiv/28-30, 22-5/8"; M91/30, 24-7/16"; Kiv/39, 22-5/8".

All in all, very similar sight pictures.

Hey, FuzzyGeff!  What are the angles at 100 yards?  This is basic geometry, I can do this!

Let's Math!  (rounded to 3 decimals).  It's just a tangent conversion since we know two legs of the triangle in question (but not the hypotenuse) and none of the angles except 90˚ where our legs meet.

1/2 the sight width / distance from eye = tangent of the angle for half the sight.

Double that and we have our angle.

Same process lets us extend the range.  Tangent of the half angle times distance gives us half the width at the target.

Why halves?  Because it's easier to calculate that way.  Trust me, I'm a draftsman.

91/30

Angular size of the rear sight notch is 0.275˚  That's 17.306" wide at 100 yards.

Angular size of the front sight is 0.130˚ (2.311 mil).  That's 8.162" wide at 100 yards.

Kiv/28-30

Angular size of the rear sight notch is 0.311˚  That's 19.521" wide at 100 yards.

Angular size of the front sight is 0.162˚ (2.880 mil).  That's 10.175" wide at 100 yards.

Kiv/39

Angular size of the rear sight notch is 0.362˚  That's 11.365" wide at 100 yards.

Angular size of the front sight is 0.151˚ (2.684 mil).  That's 9.477" wide at 100 yards.

That's not much difference at all.  Especially since shoulder to shoulder is about 24".  This is also why you learn math, to shut people up about the huge differences in things when they're really quite small.

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