recently read a couple of articles in two of the major gun mags in which the
authors spent quite a bit of time discussing the importance of ďexit pupilĒ when
evaluating scope performance. In case you didnít know, exit pupil is a term used
to ďmeasureĒ the brightness of a spotting, rifle, or pistol scope. Itís
expressed as a number in millimeters thatís supposed to represent the amount of
light exiting a scopeís eyepiece.
The concept is based on the fact that the pupil in the eye of a young,
healthy individual will dilate to approximately a maximum of 7 mmís. Of course
when the eye is dilated to its largest diameter, the maximum amount of light is
passed through the cornea to the retina. Ideally a scope should then have an
exit pupil number of 7mm for the optimum amount of brightness.
So how is exit pupil determined? Simple. Just divide the diameter of the
scopeís objective lens by the magnification. So if you have a 44 mm objective
lens on a 6 X 24 rifle scope, the exit pupil is just over 7mm at 6 power. At 24
power, the exit pupil is only 1.8mm. While 1.8mm is usable in bright sunshine,
itís not all that great on dark overcast days.
Itís interesting to note that in spite of their significantly larger
objective lenses, spotting scopes usually have exit pupil numbers much lower
than rifle/pistol scopes. Why? Because spotting scopes usually come equipped
with much higher magnifications. For instance, lets take a regular 60mm spotting
scope with a run of the mill 20 X 60 variable eyepiece. At 20 power, the exit
pupil number is 3 mm, which is ok but really not very bright at all compared to
a good rifle scope. At 60 power, itís only 1 mm, which is down right terrible.
Even if we spend bigger bucks and get a jumbo 80mm spotter, the numbers change
to only 4 and 1.3mmís respectively. (4 mmís is considered by many to be the
minimum number useful in dark, overcast conditions or twilight.)
High magnification powers not only makes the image unacceptably dark, but
resolution (the ability to see small details distinctly) also drastically
suffers. Of course, the ability to see small bullets holes at long distances is
of particular importance to us as silhouette shooters. Additionally, color
fidelity goes to the devil as well. Color fidelity isnít a big deal to a target
shooter, but itís extremely important to a hunter trying to scope a buck in the
timber or brush, or a birder trying to spot that yellow belly sap sucker in the
Considering that brightness is one of the prime considerations that
shooters use in selecting a spotting scope, you canít help but wonder why the
manufacturers insist on furnishing them with super high power eyepieces that
drastically reduce their brightness and therefore their usefulness. I recently
put that question to a very good friend who works for one of the major scope
outfits, and he replied ďbecause the public believes that when it comes to
power, more is betterĒ. He added ďThe public doesnít understand that brightness
and clarity are far more important than magnification in seeing the target
Although I own two different spotting scope with eyepieces that will go
up to 45 and 60 power respectively, theyíre always set on their lowest power
setting for maximum brightness (15 & 20X), and they work great that way. This is
especially important for myself because, although I hate to admit it, Iím past
my prime years physically and so my eyes probably aren't dilating to 7 mm any
longer. Iím probably in the 5 or 6 mm range now so I need all the brightness I
can get and itís only going to get worse.
In an ideal world, Iíd like to see someone make a 60mm spotting scope
with a power range of 8.5 X 15, and an 80mm scope with a power range of 12 X 20
power. At these power levels, brightness would just about be ideal for the scope
While exit pupil numbers might have some theoretical value, theyíre
really a very poor way to evaluate a scopeís optical brightness. Say we have two
60mm spotting scopes and both are equipped with a 15 X 45 power eyepiece. One
scope is an $69.95 discount store special made by a no name company in Lower Elbania. The other is a premium quality major brand scope selling for $500. Both
scopes have identically sized objective lenses and equal magnification powers.
Therefore, they will also have identical exit pupil numbers. Does that really
mean that both scopes have equally bright images? Absolutely not! Iím sure the
manufacturer of the inexpensive scope will brag about its exit pupil numbers in
its literature, but the relationship of those numbers to a decent optical image
is pretty tenuous at best.
So what makes the difference between the brightness of the images
produced by the two scopes? Only little things like the quality of the optical
glass, or perhaps the fact that some of the lenses on the cheap scope may not
even be glass at all, but rather plastic. The design, type, and grade of the
lenses used, and the quality or the ability of the internals to hold everything
in precise alignment are also prime issues.
Are the lenses coated? Are they multi coated? Are some of the lenses
coated or multi coated and some are not? Are all of the lenses multi coated on
both sides or on just one side. How many coatings of what materials do they
Iím making a major issue of the coatings because they are actually an
extremely important factor in determining the level of performance that a scope
will deliver. Why? Because they will actually increase light transmission above
the theoretical exit pupil number. Additionally, theyíll also increase contrast
and reduce reflections, glare, optical flare, and a number of other components
affecting the quality of the image.
All these factors and more have a tremendous impact on the brightness of
the image delivered to the eye of the observer, yet the value of all of these
features aren't addressed, and canít be addressed by over-simplified and
over-used exit pupil numbers that seem to be the darling of some. So really,
what good are these numbers? Answer - not much. The only and best way to judge
the brightness of a scope is to look through it and see for yourself what the
image looks like. If your local retailer wonít let you compare the image in a
variety of scopes that they have for sale, shop elsewhere. Check out the scopes
your friends are using and get a feel for what looks good and above all, donít
get wrapped up in exit pupil numbers.
How Important Are Spotting Scopes Anyway?
When ever you see a photo of a silhouette match in progress, what do you
notice first? Usually, the photo depicts a sea of spotting scopes with the
spotters intently peering through the various eye pieces. Oh yes, then down on
the ground you finally notice the shooters.
Spotting scopes are obviously an important or even a critical piece of
equipment in our sport. I've always felt that a good spotter with a good scope
can be worth 2 points to even a well skilled and experienced silhouette
competitor. For the less experienced and skillful, the value of the spotter
actually increases, but only if they are equipped with a good scope which allows
them to clearly see what's going on. A good spotter not only observes the
placement of the shot but also can act as a coach, teacher, advisor, or even
So why is it then, that so many shooters skimp when it comes to their
spotting scopes and hobble the effectiveness of their spotters to do their job
of helping the competitor score points? It doesn't make sense. It's not unusual
to see spotters using scopes 30+ years old whose lenses have become dim and
yellow with age and whose internals are far out of alignment from years of being
dragged and bumped around.
Then there are the discount store specials. Wanting to be open minded
about such things, I recently decided to do a review of just such a scope from a
well known company. The low priced 60mm scope was visually attractive,
waterproof, and rubber coated (even the lens caps).
The optics however were the worst that I've ever seen. At 50 yards, only
an area the size of a dime in the center of the lens could be brought into
focus, and even then, the image was dark and washed out. At 100 yards, the
area in focus was even smaller and darker still. At 200 - forget it.
Everything was a dim blur. Needless to say, I returned the scope. I got
the shock of my life however when I saw a friend of mine, a well
experienced silhouette shooter, with exactly the same scope the following
weekend. I'm sure my friend thought he was saving some bucks, but he was
also putting himself in the possible position of loosing points in all his
so drop by to see what the current situation is.
As a guide, take a look at the quality of the spotting scopes that our
champion silhouette shooters are using. Everyone is naturally interested
in their guns and loads, but also look at their spotting scopes. I doubt
if you'll see that very many, if any at all, are impeding the ability of
their spotters by using junk scopes. Follow their example and you won't be
TASCO Says ďIímmmm BaaaaackĒ
The Tasco name and all its intellectual property has been purchased by
Bushnell. Evidently, Tasco had a significant presence in Europe,
Australia, and Canada and so Bushnellís purchase will strengthen its
position in those marketplaces.
As of this date (Aug 7th), Bushnell is evaluating Tascoís product line up
and is deciding what itís going to keep and what itís not. Bushnell didnít
buy any of Tascoís remaining stock, equipment, or facilities. Bushnell is
also revamping Tascoís web site
The best news is that if you already have a Tasco product that requires
service, ďspecial arrangements have been madeĒ with ABO USA to take care
of those problems. Call them at 305-860-4858 for more info. ABO USA is not
connected in any way with Bushnell, and Bushnell states it definitely has
not picked up any obligation to service any Tasco product made prior to
Tightening Up a Freedom Arms Revolver
My good friend Dr. Jim Williams just bought a used FA 353 and has recently
been playing with it developing loads. He reports that it seems to like
16.2 grains of H110 with a Speer 180 silhouette bullet.
While cleaning it after a session at the range, he got the vague
impression that the grip felt a little loose. Taking the grip in one hand
and twisting the barrel in the other, sure enough, he felt a little
movement. Investigating further, he found that the two screws located
under the hammer and the one screw on the underside, forward of the
trigger guard, were indeed loose. It was an easy job to tighten them up
and everything was fine once more. He also reported that the little bit of
trigger creep heíd been experiencing completely disappeared.
Is this an unusual situation? In my experience no. On both my 44 and 357,
I would find that these screws would loosen up from recoil from time to
time. A simple periodic check and snug with a quality screwdriver is all
thatís needed to correct the situation. Itís not a big deal but you want
to keep those screws tight for the best accuracy.
National Reloading Manufacturers Association
As the name implies, this is a industry association made up of all the
manufacturers that make reloading equipment, components, and accessories.
Itís fundamental mission is to encourage shooters to reload.
(Itís amazing how few actually do.) NRMA does this mainly by providing
information and literature to budding reloader's.
They also have a list of 670 NRA certified reloading instructors that
teach classes on safe reloading. Each instructor is listed by name,
location, zip code and telephone number.
NRMA also has a deal where you can get a bundle of materials called the
Catalog of Catalogs. It contains five reloading guides, two mail order
catalogs from reloading suppliers, seven component and equipment catalogs,
and a safety guide for only $10. This bale of catalogs weighs in at over
three pounds and has just about all the info anyone would need to get
started in reloading whether about powder, bullets, equipment, or
whatever. To get the package, just send a check or money order to NRMA, 1
Centerpointe Dr, Suite 300, Lake Oswego, OR, 97035 and ask for the Catalog
of Catalogs. Going through all this stuff will keep you busy for a long
Proper Mold Temperature
Determining proper mold temperature is something of an art. As most
bullet casters are aware, mold temperature is critical to the casting of
bullets that are properly filled out and without imperfections. Just like
the porridge in the story of Goldilocks and The Three Bears, the
temperature of the mold has to be ďjust rightĒ - neither too hot or too
Of the two conditions, being too cool is probably the most vexing. If the
mold is too cool, the bullets will come out wrinkled, indented, and
looking generally strange. Even when the bullet seems to be normal, the
surface can have an uneven appearance in color. This is an indication that
the internal density of the bullet is probably not uniform.
The most subtle problem occurs when the mold reaches a temperature that
is close to the correct temperature but still not quite there. Under a
casual examination, the bullets will appear to be ok. However a close,
critical examination will reveal faint, but very real flaws. At this point
the casual caster might be fooled into thinking that the proper
temperature has been reached and will accept bullets that are actually
Since we donít have an easy means of directly measuring the temperature
of the mold itself, how do we determine when it becomes hot enough to
produce quality bullets. Actually there is a very simple, but indirect way
to determine when the correct temperature has been reached. Examine the
underside of the sprue. For the uninitiated, the sprue is the puddle of
molten lead that accumulates on the top of the mold when itís poured down
into to the cavities. Once it solidifies, the caster hits the sprue plate
with a wood mallet or whatever, and the now solid lead puddle is sheared
If the mold has not reached the proper temperature, the bottom side of
the sprue will be wrinkled with lines or mini crevices meandering across
its surface. However, when the mold has reached the appropriate
temperature, the bottom of the sprue will be perfectly smooth without any
lines what so ever. Flawless bullets will now be dropping out of the mold.
We now have to worry about the mold getting too hot from continuous use.
Gun writers with lots of money recommend using two of the same mold or
perhaps two different molds, alternating between one and the other so
neither gets overheated. I donít like this method as it takes longer to
get the two molds up to the correct temperature. This can be shortened
somewhat by pre-heating the molds on the side of the electric pot while
itís coming up to temperature and melting down your lead. Drape a piece of
aluminum foil over the top of the pot to trap the heat when doing so. This
method works well with a single mold also. Never the less, getting two
molds up to the right temperature is a pain.
Rather than using the dual mold method, I prefer to use a small fan on
the loading bench to prevent my molds from overheating. When I notice that
the bullets are looking a little frosty, or perhaps developing ďwhiskersĒ
on the side, or the sprue mark on the bottom of the bullets doesnít have a
smooth shear across, Iíll just hold the mold in front of the fan for about
5 seconds. That takes care of the situation with no problems. The fan,
which I bought for $1 at a flea market, also helps to keep me cool,
increases air circulation and disperses lead fumes.
Follow these simple procedures, and youíll be as content as Goldilocks
eating porridge thatís juuuust right.