From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Correcting My Front Sight
Organization: Lawrence Berkeley Laboratory

marko@xcaret.hf.intel.com (Mark O'Shea) writes:

#My .45 (Some of you may remember I shoot IPSC with it) shoots a tad low.
.........
#Not ever having done this before, I am wondering how to go about it.
........

I'm certain that this doesn't apply in your case but: for the inexperienced
shooter, have someone who is experienced shoot the gun to verify that the gun 
shoots low: hate to have you adjust the sights to compensate for a flinch.  
It's been done, you know.

If it shoots too low, your front sight is too high.  It's simple enough to
take care of the problem once you know how much to take off if you have or
can borrow some dial calipers.  First, are you sighting in for 25 yards or
50 yards?  Let's say 25 yards (=900 inches).  How low is the impact?  Let's
say 1.5 inches.  How far from the back of your front sight to the back of
your rear sight?  Let's say 6.5 inches.  Then the amount you want to remove
from your front sight is (6.5/900)*1.5 = .011 inches.  Now wrap the calipers
around the muzzle so you can read the height from the bottom of the slide to
the top of the front sight.  Subtract .011" from that figure to get your
desired height.  Now get a smooth flat file about 1.5" wide and 12 inches long
and tape shim stock to the first four inches of the file nearest the file's
handle.  This is the end of the file you rest on the rear sight so that
when you whittle on the top of the front sight, the top of the front sight
will be coplanar with the top of the rear sight.

If you haven't used dial calipers before, take several readings to ensure
that you can get a consistent reading.  The above directions are for a field 
correction.  If you have access to a mill, just clamp the slide in the vise
using paper or copper shim stock to protect the finish.  Make sure the slide
is tilted in the vise so the top of the front sight is maybe a 16th of an inch 
above the top of the rear sight.  Then take a cut until the rear of the front 
sight cleans up, dial in the .011 on the knee and cut 'er off - nothin' to it. 
If you don't tilt it up, you may tilt it down and then you get low-angle
reflections off the top of the front sight and you don't know where the top 
is anymore.

There is an advantage to doing the field correction: you can do it at the
range and then if you're unsure of yourself, you can take a few test shots
along the way as you remove metal.

John Bercovitz            JHBercovitz@lbl.gov

PS:  For those of you whose guns shoot too high, that's an easy correction:
Just get a long barrel link and stick it in the gun to raise the rear of the
barrel.  Use the distance from the barrel bushing to the link instead of
the sight radius in the above calculation.  Take a small rat tail file with
you so you can move the link's holes closer together by slotting until 
you're hitting dead on.  A small, portable, vise to hold the link while you
file on it is also nice.  Calipers are used here also to measure the meat
between the link's holes.

JB