A Discerning Look Inside The Rifl escope:
Why Guns Fail To Remain Sighted Norman E. Johnson
modern day rifle performance and pleasure than any other part of shoot- ing. It also helps to reduce the human element from the shooting equation. The modern day consumer has become used to the latest in technology in many areas, and we’re being offered the latest in scope sight technology from all sides as well. Supreme lenses, laser/computer rangefi nders, lighted reticles, a maze of rangefi nding reticles, innovative paral- lax removal, bullet trajectory indicators, even electronic power settings. Surely audible messages from the scope can’t be far behind. Seems today’s consumer wants it all, and if things aren’t just right, there’s often hell to pay. Yet few things continue to cause the serious shooter more concerns than to take a rifl e from the rack, whether it has sat a year or a day, only to fi nd it has failed to remain sighted – or to see bullets crawl around on target as the scope is sighted in. Truth be told, these remain a major concern with the modern-day scope user. In this treatise I will cover in detail
A
that which I have determined to be the more important and provoking internal rifl escope problems leading to scope reticle instability. In a separate article I will relate to problems specifi c to scope mounting, action bedding, and things that cause a rifl e to lose its sight-in…but fi rst, let’s take a real close look inside the scope itself. Few issues are more disconcerting
to a hunter/shooter than a gun that fails to remain sighted-in, and this includes nervous reticles that wander around while shooting. This insidious, bewil- dering plight can include rifl es, hand- guns, shotguns, or most any kind of gun that wears a scope sight, but especially that rifl e you may be depending on. Scope problems may well be the
culprit for a surprising number of one’s missed shots, particularly at longer
rguably, the telescopic gun- sight has done more to affect
This picture of a sectioned variable-power scope shows the erector lens
zoom system withdrawn from the turret where the erector tube is adjusted for lateral and vertical movement (windage and elevation). The spiral zoom system is positioned within the erector tube. The erector tube is attached to the indexed power adjustment collar (right),
where it pivots as windage and elevation adjustments are made. At far left is the open tube where the side-focus parallax correction system was removed. There are many moving parts hidden within a modern telescopic sight that
can contribute to scope reticle instability, all dependent on the mechanical tolerance built into the scope. Few scopes are totally free of some optical/ mechanical error within the system.
Here the erector lens tube is shown, adjusted at extreme left windage and
elevation with the erector lens pushed at maximum against the triangularly positioned return spring. The screw surfaces tend to make somewhat out-of- square surface contact with the erector tube in this extreme position. As is obvious, a 30mm scope tube would provide greater elevation and windage adjustment. The zoom lens is forward in the spiral tube on this picture. There is very little room for tolerance error in any of the moving parts pictured here. This is one of the areas where scope break-in can have a positive outcome.
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