From: jgd@dixie.com (John De Armond)
Newsgroups: rec.guns
Subject: Re: T/C pistol iron sight question...
Date: 19 Nov 92 15:06:23 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.

minh@inst-sun1.jpl.nasa.gov (Minh Lang) writes:

No one else jumped in so I'll give it a shot.

#Hi, I have a question that I would appreciate
#any help. I have a T/C 10" 44 magnum with
#a factory iron sight. Using an electronic
#caliper, I measured the rear sight's height
#at different clicks and this is what I got:
#- with the rear sight all the way down, it's
#   2.020 inches.
#- with 5 clicks up, 2.045"
#- with 10 clicks up, 2.063"
#- with 15 clicks up, 2.084"
#- with 20 clicks up, 2.108"
#- with 25 clicks up, 2.128"
#The click adjustments are not consistent. I am wondering
#is this a common problem wihth the factory iron sight?

Yep.  That's why many of us production class Silhouette shooters lap the
clicker on the sight and then keep a little 3X5 card with sight 
settings on it.  The big concern is repeatability, something the T/C
sight does quite well, particularly after being lapped.

#If it is, is there any iron sight that gives consistent
#clicks and it can fit the T/C without drilling and tapping?
#(Such as Williams ro Lyman?)

Nial Tuvel (NiTu Machine Tools, 404 986 9741) who is the Ga State Silhouette
champ, makes and sells a fantastic silhouette sight.  The sight floats
on 2 hardened and chromed pins and the lead screw is a very fine pitch
hardened affair.  The click detents are actually tiny spring balls like
used on machine tools.  One click is worth a half inch at 200 meters on
a 14" barrel.  The blade is hooded.  I think he gets $120 for it.  He'll 
want to install them for you.  Don't let him.  As good a gunsmith and 
machinist as he is, I've seen way too many sights come from his shop mounted 
crooked, mine included.  If you buy the sight, put it on yourself.

#Also, is there an accurate way of calculating the relation
#between MOA and sight click? (In other words, giving
#the sight radius, sight height (and adjustment per click),
#muzzle velocity, can we accurately calculate the
#MOA/click? I tried to calculate it using trigonometry
#but it seems the result is too far from being accurate
#after I tested in the range).

you can compute it by simply using the ratio of distance between
the sights to the distance between the front sight and the target.
Problem is, you can't measure the sight height accurately enough.
Consider:  1 inch of movement at the target is 

1" * ( 14" sight distance / 67,200 inches (200 yards)) = 0.000208 inches

(That is impressive to think that people can hold to that accuracy :-)
The simple calculation does not take into account the dynamic effects
that may be much more significant.  For example, if you elevate the shot
slightly, you are holding the gun at an ever so slightly different angle.
This means the recoil force vector is slightly different which causes 
the muzzle to move slightly differently before the bullet exits.  
Computing even a ballpark figure is beyond my matchbook calculations
here but you should be aware of 'em.  

The only thing you really need to worry about is whether the sight is
repeatable (the T/C's is with a bit of work) and whether the clicks
are fine enough resolution (The T/C's are not.)

John

-- 
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