with my rifl es, along with much im- proved handloading, there still were too many unexplained sighting problems, evidenced by the increasing number of shooters coming to my shop for help. At this time I made a more serious effort to fi nd out why some of the scoped rifl es were plainly not remaining sighted. By then I had some pretty so-
phisticated shop and test equipment to measure tolerances and discover rifl e and scope related problems. I later de- signed and built an instrument to test scopes which revealed some frailties surrounding the scope that a shooter ordinarily wouldn’t think of. I even di- sected a few scopes in the process. The results of these fi rst tests culminated in an article published in the January 1992 RIFLE Magazine, titled: “Test Your Rifl e Scope,” and was later voted the win- ner of the 1992 Leica Writing Award. Leica thought the article was especially informative because it dealt with little known and rarely discussed limitations inherent in all rifl escopes. So, as I delved more seriously into
the interrelated scope problems, a paral- lelism was apparent between the scope and its critical internal function with respect to rifl es not remaining sighted- in. Reasons both simple and complex would be studied. LET’S CRAWL EVEN MORE DEEPLY INSIDE THE SCOPE
At this time we will look inside
the typical rifl e scope and cover some of the major issues related to the variable power scope with parallax correction. I have provided some pictures to help in my descriptions of some of these problem-related issues. In the modern-day scope, there are
many moving parts – many of which can cause the scope reticle to be unstable and shift position. The higher the quality of the scope, the closer the tolerance of moving parts is likely to be. However, as the precision machinist would defi ne it, we are still stacking tolerances, which is essentially dealing with the variance permitted in maintaining a specifi c di- mension while assembling parts togeth- er as a unit, and this includes all scopes. There are no specifi c tolerance specifi ca- tions whereby the scope manufacturers must adhere to. The old saw, “You get what you pay for,” does not always hold true either. My ongoing tests revealed problems associated with some higher
cost scopes while other seemingly lower quality scopes came through without a hitch. But the odds do favor the better known brands over the cheaper ones. Yet, how many average hunters and shooters can justify paying almost as much, or more, for a scope and mount- ing system as they would for the rifl e it’s being mounted on. Therefore, you must work with that which you have, along with its limitations, and these subtle nuances must be understood. As we peer closely into a rifle
scope looking for gremlins, let’s fi rst look at the way the crosshairs (reticle) are controlled or adjusted in sighting-in a rifl e. The erector tube, which is es- sentially a scope within a scope, houses a lens cell, including the reticle. The erector tube is pivotally anchored at one end, normally at the rear, aligned with the objective lens at the front, and the ocular lens at the rear. As the eye peers through the scope, the reticle, in its various forms, is in the path of view … essentially superimposed over an otherwise clear view of what we are seeing. Then, from its pivotal anchor point forward, about four inches, the front of the erector tube passes along the side of the scope adjustment turrets. Here it is supported near the end from below by a leaf spring which pushes it triangularly upward against the wind- age and elevation adjustment screws located directly above and at the right side of the turrets. The fi ne adjusting screws are threaded through each tur- ret with external graduated adjusting knobs. Then, as each adjusting knob is rotated clockwise, it puts increased pres- sure on the front or side of the erector lens tube, thereby causing it to move the reticle across the viewing fi eld, as a unit, against the lateral or vertical force of the single leaf spring. This produces both downward and left bullet impact shift on target. Then, as each knob is turned counter clockwise, the thrust spring, from below, causes the erector lens tube to follow the direction of the screws and move bullet point of impact upward and to the right. These adjust- ments are a vulnerable area, common to many scopes for sighting problems. Benchrest shooters readily agree that the scope sight is one of the weakest links in maintaining a high degree of accuracy and reticle stability.
..and these guys are in-the-know.
Here are the comparative results of the lower priced Barska 6.5-20x scope pitted against a much higher rated Nitrex 6-20x scope. These quite remarkable groups were shot at 100 yards with a Model 700 Remington rifle equipped with a Broughton barrel in caliber 270 Winchester using 140-grain Berger bullets. Following the aforementioned scope therapy, groups made with the Barska scope paralleled those of the Nitrex scope. As a further test of the scopes for the 16x groups, the power collar was turned from a lower setting to 16x before each shot. Here I was essentially using the rifl e to test the scopes.
Initially I had selected 18 scopes
for this evaluation, including both variable and fixed power types. But the evaluation process grew to more than 10 times this number over the next two decades. I also had improved my process of evaluating scopes. In the interim, scores of new scopes were being introduced to the marketplace, including a seemingly large number of new companies. You just turn around and a new scope brand enters the mar- ketplace. But as I indicated earlier, the more things changed, the more they seemed to stay the same. The scope still remains our only means of better seeing and hitting on target. Yet, in the area of reticle (erector tube) adjustment stabil- ity, obvious problems continue in far too many scopes, and this includes no small number of those in the mid-to-upper
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