From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: scopes/distortion/rings
Organization: Hewlett-Packard Fort Collins Site

Z. Ohanian (zareh@utcc.utoronto.ca) wrote:

:  ..... while talking about reticles, there
:  is NO way that the reticle will bend, they are mounted
:  on a rings by themselves and are wire, the little change
:  in dimension will be compensated by the tension on the wire
:  ( if wire type reticle, as %80 of scopes are,etched reticles are
:  expensive to make and are immune to physical distortion,
:  to little degree that

I've had 4 scopes (2 of 'em Leupolds) that had their wire reticules
bent.  As the horizontally split ring was tightened near the
eyepiece, the vertical compression of the main tube squeezed the
round reticule cell in the same direction.  That made the horizontal
distance across the reticule cell longer.  Which stretched the
horizontal wire.  As the split rings were loosened, the oval-shaped
reticule cell returned to a round shape, but the stretched horizontal
reticule wire now sagged down at its middle.  Inverting the scope and
tapping it a bit caused the upward-bowed horizontal wire to flop down
and reverse its position.

So, I think the reticule can bend if it's been stretched beyond its
elastic limits which isn't very much considering the metal used.

BB

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: Rubberized scopes: Questions
Organization: Hewlett-Packard Fort Collins Site

Gary Coffman (gary@ke4zv.atl.ga.us) wrote:

: It's for the same reason you put rubber tires on your car instead of
: running on the steel rims. The rubber's compliance reduces the peak
: G forces on the optics when the scope is slammed against a rock or
: other hard surface out in the field.

Actually, I use rubber tires because they have better traction than my
aluminum rims on car A and steel rims on car B.  I'm not interested in
reducing G forces with tires, my vehicle's shock absorbers do a great
job at that.

Having seen several rubber-coated rifle scopes damaged beyond use by their
`slamming' against a variety of hard things, I convinced that coating is
a marketing ploy, not a useful one.  Considering that it doesn't take much
force to bend an aluminum tubed rifle scope out of whack by a bump, the
coating on the outside will not and does not prevent damaging the scope
past non-usability.

I have intentionally subjected aluminum tubed scopes to impacts that are
far short of what's created by dropping a rifled scope upside down onto
the ground.  They easily got more than 10 MOA out of alignment.  You can't
put enough rubbery coating on a scope to prevent such damage; if so, the
coating would have to be about 5 inches thick.

To say nothing of Leupold's aluminum tubed wonders that, when the rear
scope mount ring is placed close to the eyepiece's lock ring, tightening
it too much will distort the scope tube which couples directly to the
reticule cell and results in stretching the horizontal reticule element
so much that it flops around comming to rest at different places vertically,
then when the mount is removed, that reticule element droops downwards at
its middle.

Recoil from rifles is directly imparted to optics in a scope.  Those forces
are much higher than what dropping the rifle 3 feet would produce.  But
the recoil forces are mostly along the scope's optical axis.  Which lends one
to believe that most scope damage comes from recoil.  If you calculate the
forces an 8-pound rifle puts on one end of a scope should it be dropped
just two feet, I think you'll find out that no amount of rubbery coating
will keep the scope mechanically/optically intact.  Especially those whose
ends are 4 or more inches away from the closest mount.

If one does some tests and find out the MOA deviation even a small amount of
pressure to the objective lens end at right angles to its optical axis
creates, one will soon understand what their `ruggedness index' really is;
rubbery coated or not, steel or aluminum tubed.

BB

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Subject: Re: Rubberized scopes: Questions
Organization: Hewlett-Packard Fort Collins Site

Randy Howard (jrh@mustang.us.dell.com) wrote about my comments below:

:  >To say nothing of Leupold's aluminum tubed wonders that, when the rear
:  >scope mount ring is placed close to the eyepiece's lock ring, tightening
:  >it too much will distort the scope tube which couples directly to the
:  >reticule cell and results in stretching the horizontal reticule element
:  >so much that it flops around comming to rest at different places vertically,
:  >then when the mount is removed, that reticule element droops downwards at
:  >its middle.


These words:

: Hang on, aren't you the same Bart Bobbitt that was writing recently about
: how wonderful Leupold scopes are?  Are you the real BB, or an impostor?
: Someone must have stolen his password.

I believe it is everyone's responsibility to learn what the capabilities,
and limitations, are regarding everything they use.  Otherwise, they will
eventually get into trouble in attaining their objectives using things in
ways they are not intended to be used.  Leupold scopes are no exception.
They are indeed what I said they are: great scopes.  But only when used
within their capability bandwidth.  But then that premise applies to most
everything, doesn't it?

Many other rifle scopes have this same limitation.  If one knows how scopes
are constructed, one will never put a mounting ring around the reticule
cell's position on scopes whose main tubes are made from aluminum.
I've seen dozens of aluminum-tubed scopes so ruined; their owners had
no idea what they were doing when they used a lot of force to tighten the
ring screws with gusto on aluminum-tubed scopes.

I wonder if anybody has figured out why I like steel-tubed Weaver T models.

Of course, one could be careful of where the rings attach to the scope, but
what if the scope's application requires a ring/mount to be attached around
the reticule's mount position?  Betcha there's a lot of scopes out there
whose repeatability in elevation is pretty bad.

BB (yes, the same one as before)

From: bartb@hpfcla.fc.hp.com (Bart Bobbitt)
Newsgroups: rec.guns
Subject: Re: Rubberized scopes: Questions
Date: 15 Apr 1994 12:49:50 -0400

: So where is the reticule cell?  It must be somewhat around the
: adjustment knobs on the scope, since the knobs surely are there to move
: the reticule.  

Rifle scope reticules are typically about 2 inches in front of the 
eyepiece lens group.  Or very near the lock ring that locks the eyepiece
and keeps it from turning.  This is because the adjustments move the
front end of an internal tube called the erector lens assembly.  
The back end of this internal tube is held fixed and the adjustments
move its front end which moves the image it forms on the reticule.
This is how reticules stay centered; the target's image is moved about
the reticule.

As the eyepiece has a focal length of about 2 inches, the reticule must
be about 2 inches in front of it so the eyepiece can focus on both 
the reticule and the target image formed there.

There are a few scopes whose reticule is at the front of the erector
tube at the focal plane of the objective lens.  These scopes are such
that the reticule changes size as their magnification is changes.  With
the reticule at the eyepiece's focal point, it doesn't change with 
magnification.

Older scopes had their reticules at the adjustment turret but not
part of the erector lens tube.  Which is why the reticule moved around
in the field of view when adjustments were made.

BB