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Abbas
31-12-2008, 02:00 PM
This is a very informative article. I recommend anyone interested in Telescopic sights to read it.


There is an old iron sight axiom that goes something like this: The better you can see your sights and your target, the more accurately you will shoot. But, that is only true as long as your sights are pointing in the same place from one shot to the next. Even though telescopic sights allow you to apparently see much better, there are aspects to them that create new sighting problems the old iron sights didn't have. And of course, scopes need to be pointing in the same place from one shot to the next just like iron sights!


What determines if a scope shoots accurately?

Parallax Error; Adjustment Consistency; and a Solid, Well Aligned Mounting System.


What determines how well you can see with a scope?

Objective Size, Lens Quality, and Lens Coatings. For handguns, Eye Relief is a serious consideration. These are the topics I’ll address in this Technical Report.


PARALLAX ERROR - Parallax error is when changing positions of your eye will change the point of aim of your scope. The error is related to the distance the target is from you. Most sporting rifle scopes are set to be Parallax Error-Free at 100 yards. That is, when aiming through your scope at a target 100 yards away, the point of aim stays the same regardless of the position of your eye.


TEST FOR PARALLAX ERROR - It’s pretty simple (and enlightening!) to test your scope for parallax error. Position your scope or scoped firearm in sandbags so that it is aiming at a 100 yard target. Now, without touching the gun or the scope, move your head from side to side while looking through the scope. If the crosshair moves around on the target, you’re seeing parallax error at that distance. How much error depends on how much movement. I’ve seen some scopes where the movement was 4-6inches! To find the distance where your scope is parallax error-free, do this experiment at 25, 50, 75, 100, and 125 yards. The distance where it is error free will also be the distance at which you shoot most accurately.


PARALLAX ADJUSTABLE SCOPES - Scopes with an “adjustable objective” (AO) allow you to set the distance at which they are parallax error-free. These scopes are also designated as Parallax Adjustable (PA), Side Focusing (SF), etc. It's misleading to call this feature "focusing" because its really parallax correction. Its also important to note that the distance markings on the parallax adjustment are quite often NOT ACCURATE. This is partly due to the scope user's own eye optics, but also due to changes within the scope from one magnification setting to the next. In fact, some high end scope companies have addressed this by not putting specific distances on the parallax adjustment. Instead, they say use the test (above) to find the point of zero parallax error for each distance yourself. Use a silver or white paint pen to mark the positions. When all other things are equal, adjustable parallax can make even a cheap scope a bargain in the ability to dial out parallax error when aiming.


HOW CRITICAL IS PARALLAX? - For pinpoint aiming purposes, parallax error is most critical at under 100 yard distances. And this is why most rifle scopes are set to be parallax error free at 100 yards. At under 100 yards, BIG game are large enough that parallax won’t throw you too far off your aiming point. And beyond 100 yards, the error is simply less for the difference in distance. Adjustable Parallax scopes have a lot of adjustment under 100 yards but just a little as range increases over 100 yards. So, if your scope tests parallax error-free at 100 yards, it is going to work just fine for most big game hunting situations. But, if it shows a lot of parallax error at 100 yards, it is simply not going to shoot accurately and reliably. And, if you're hunting SMALL game at distances over 100 yards (ie. varmints and prairie dogs) the ability to dial out parallax error becomes a necessity.


ADJUSTMENT CONSISTENCY - It stands to reason that if your scope reticle doesn’t stay at the same point of adjustment, it will not give you the same point of aim from one shot to the next. Scopes adjust the reticle by screws which push the reticle tube against a leaf spring. From one shot to the next, recoil may shift the reticle tube against the spring. As long as it returns to the same position, the scope will keep the same point of aim. But if it moves, your scope will not shoot accurately. A good scope will have little or no recoil movement of the reticle tube and adjustments will stay consistent.
Sometimes the point of impact can change as you zoom the magnification on a variable scope.


SOLID WELL ALIGNED MOUNTING SYSTEM - If your scope moves in your mount, it will change your point of aim. If your scope is tensioned, bent, twisted or torqued in your mount, it is just waiting for any influence to change your point of aim... temperature, a slight bump, a little recoil, or even the pressure you impart on it by twisting the zoom or adjusting the objective. Finally, if your scope mount doesn’t align your scope with the direction your muzzle is pointing, your reticle adjustments will have to be pushed to outside extremes to sight in your point of aim with your point of impact. I became aware of the importance of scope mounts to accurate shooting when we were developing our Tri-Force scope mounts for handguns. These mounts use three rings and you can really spot bad ring alignment when a scope has to make contact with three mounting points. Generally speaking, rings that are machined show a lot of alignment problems. Maybe that’s why we now hear about “Lapping” of rings in scope installations. What we found was that we got the best alignment from rings manufactured by extrusion processes. Extrusion is very much like the Play-Dough Factory little kids use. Aluminum is pressed through a die and comes out a big long tube shaped like a scope ring. Individual rings are cut from this “extrusion”. Since it all comes out of the same die, alignment from one ring to the next is identical! The same holds true for scope mounting bases. There are folks who want steel scope mounts just because they trust steel more than aluminum. But steel can’t be extruded... it has to be molded or machined... neither of which process works as well as extrusion for alignment purposes. The truth is, extruded aluminum scope mounts hold scopes super solid, they don’t weigh a ton, and they offer the alignment advantage of having been made by extrusion.


OBJECTIVE SIZE - Everything we see is really just “light” being reflected off objects in our field of view. The less light there is, the less we see. A term you will see quite often associated with optics is “light gathering”. It refers to the ability of an optical device to capture as much light as possible. It is a common misconception that magnification is what allows us to see more through a telescope. But magnification only makes things bigger. In fact, magnification reduces the field of view, reducing the amount of reflected light, and letting you see less! Try it sometime with a really high powered zoom rifle scope. The higher you zoom, the darker your sight picture becomes! Generally speaking, the larger the objective (front) lens of a scope, the more light it can gather, and the more you can see. This is the reasoning behind the 50mm scopes we see being offered in recent years. As with anything, the size of the objective can reach a point where the improvement isn’t significant compared to other optical considerations. For example, I’m convinced that a 50mm objective only makes a significant difference over a 40mm when scopes are used at extreme magnifications of 14-36X.


LENS QUALITY - Did you know that one of the chief exports from Viet Nam is sand? Sand is what you make glass out of, and Viet Nam has such exceptionally pure sand that other countries actually buy theirs rather than purify their own! There are a lot of scope lenses made from Vietnamese sand/glass and that also explains why there are so many fine optics manufactured in Asian countries (And yes, there are some absolute junk optics from there, too). It stands to reason that the optical clarity of the lenses in a telescopic sight will have a lot to do with how much light is gathered... and how much you can see. Poor quality glass will also present distortions and distractions. “Chromatic Aberration” is a distortion you’ll see around the edges as you look through a low quality scope. Combine a distortion with some parallax error and you’ll have a real tough time shooting accurately. Good quality glass makes a scope cost more. But you don’t have to pay an arm and a leg.


LENS COATINGS - Being highly polished, a glass lens not only gathers light... it also reflects it away. And the more that is reflected away, the less you can see through the scope. Lens coatings are used to reduce reflection and improve light gathering. As you look at a coated lens from the side, you will see a colored hue to what is reflected in the lens face. Most coating hues are blue. Some are green. And some are pinkish. Some manufacturers have enhanced coating systems that use multiple coating layers and materials to give even better light gathering and the least possible reflection. Suffice it to say, lens coatings make such a big difference that no high quality optics are offered without them.


30mm Tubes vs. 1 Inch Tubes - In recent years we’ve seen the introduction of scopes with 30mm tubes. Presumably if a larger objective gathers more light, a larger tube should be a good idea, too. We sold quite a number of Swift 2.5-10X50mm with a 30mm tube and have to say it was one heck of a nice scope with a brilliant, clear image. It was discontinued however... maybe too expensive to make. The main consideration in a 30mm tube scope is that you will need 30mm rings.


EYE RELIEF IN HANDGUN SCOPES - Since a handgun is held at arms length away from your sighting eye, the “eye relief” of a handgun scope is set for a longer distance than it is on a rifle scope. What a lot of folks don’t realize is that variable power (zoom-magnification) scopes change their eye relief as the magnification zooms from low to high. A scope that is an arms length away at 2-3X has to be sucked back to 10-11 inches away on 7-9X. Since a handgunner is most accurate when he maintains a consistent hold, having to change his hold for a variable scope is bad for accuracy. With the limited field of view and reduced eye relief of handgun scopes in the over 7X magnification, I recommend them primarily for bench rest target and varmint shooting.


PERSONAL PREFERENCES - I do recommend the scopes we sell but it isn't a prejudice. First, any scope brand that has a lot of defects doesn't stay in our line very long. We don't like problems anymore than you do! Second, I like to get as much quality as I can for my money and figure you do, too. With that in mind, here are my thoughts on what to consider when purchasing a scope:

50mm Objectives - These are most significant when using highest magnification scopes of the 18X-36X variety. However, they certainly don't hurt when you're zoomed up into 12-16X either.

40mm Objectives - The best value for features and quality on scopes with magnifications up to 18X.

Parallax Adjustable - I highly recommend it when the other features of a scope meet with your needs.

Magnification - I hunt deer in Minnesota using scopes set for 2-4X in the woods. I hunt Antelope in Montana using scopes set from 4-12X on the open range. Anything over 12X and I lose my ability to find what I’m aiming at as I shoulder my rifle. So, a 4-12X40mm is the best all-around scope for me. I like this magnification range for Varmint shooting as well. For targets and group shooting, I like scopes that zoom up close... 18-32X. For a handgun, 2X is best for off-hand and up to 6X for bench shooting.

Swift SRP Premier Scopes - Superb. As good or awfully close to Leupold and Burris for a lot less money. The optics, lens coatings, durability, and repeatability on these scopes is unsurpassed.

Mueller Scopes - Made from the finest Japanese glass with high end German lens coatings. These scopes are famous for their unique reticles as well as superb optics at a reasonable price.

Brown 97D Riflescope - Our 97D 4-12x40mm Riflescope evolved out of our extensive experience at selling Swift Premier SRP and Mueller APV riflescopes. We combined the extra features of a Swift (fast focus eyepiece and dust covered target knobs) with the superior optics and mechanical reliability of a Mueller (clarity, coatings, and crisp repeatable clicks). The 97D Riflescope sells for quite a bit less than the Swift and only a little more than the Mueller. Click Here to read more about it.

Bushnell - Now combined with Bausch and Lomb. Their Elite 3200 and 4200 lines of scopes are top quality optics at a reasonable price. Same with their Trophy line.

Tasco - Surprisingly good even on our least expensive ones... very few complaints or defects. We sold thousands of a special edition 6-18X42mm scope with target knobs and parallax adjustment for only $74 and heard many good comments and had almost no problems with it. The Tasco Mildot scopes are excellent quality for a low price.


PERSONAL CHOICE RIFLE SCOPE- Over the years I've shot some of the tightest groups of my life while using the Swift 676 Premier 4-12 X 40mm P/A and the Swift 672 Premier 6-18 X 50mm P/A. I've also whacked a 5 inch steel disk over and over from 325 yards away using a Tasco 2.5-10X Mil Dot scope. I still have in my memory a one shot antelope kill, through the heart at 264 yards with my Model 97D Rifle in 6.5 BRM... The scope was an Elite 3000 4-12X40mm (New ones are Elite 3200). I have a similar 271 yard one-shot Antelope kill using the Swift 205-676M SRP 4-12X40. For the last few years, I've been using Pentax and Mueller scopes. Made a 270+ yard shot with the Pentax 4.5-14X42mm Ballistic Plex riflescope with my Encore in 6.5mm BRM. With my 97D Falling Block Rifle, I have gone from hunting Antelope and prairie dogs with the Mueller APV 4.5-14X40mm to hunting more recently with evolving prototypes of our Model 97D 4-12X40mm Riflescope. Last Year (2007) I made the longest and best placed Antelope shot of my life... right through the heart at 312 yards. And earlier in the year that same 97D prototype riflescope had me hitting prairie dogs farther out and more consistently than I had ever shot before. So you might understand why I recommend the Brown 97D Riflescope!

When 2-7X is Best - If you hunt in the Minnesota woods, a Premier 2-7X40mm Wide Angle scope such as the Swift 205-658M would be an excellent choice. At 2X magnification you can find your target fast when its up close, in the brush, and moving. The 40mm objective captures a HUGE amount of light at the low magnification range. And you generally wouldn't need more than 7X magnification for shots in open areas.


PERSONAL CHOICE HANDGUN SCOPE - The Bushnell Elite 3200 2-6X gives me the same 2X eye relief when I zoom it up to 6X magnification.


Author: Eben Brown

TAREEN
19-02-2009, 10:57 AM
May I suggest a reading from Chuck Hawks:

http://www.chuckhawks.com/scope_magnification_rifle_caliber.htm

ch shahnawaz arain
20-04-2013, 09:43 PM
i m looking for leupold mark IV or leupold 55000 scope for my .243.plz update the price and availability any part of county.thanks