Scope malfunctions

[Doc]

I have never seen a diagram of the internals of a typical scope, so I am a bit curious about what the most common inconsistancy problems could be. It would seem to me that once the components were assembled and locked down, it would be impossible for them to be anything but consistant regardless of the quality of the scope. However, I have definitely seen scopes that would spray impact points all over the place regardless of the abilities of the shooter. In fact, my brother-in-law, who is a pretty darn good shooter recently had a scope that had been shooting great for him for years, suddenly develop a condition where the reticle was rotating (both cw and ccw). I'm not talking about just a little, but at one point was almost 45 degrees off. He was still able to place the slug in the middle of the target, but the potential inaccuracies were apparent. Since this happened right in the middle of deer season, we made a quick trip to Gander Mountain and bought a Nikon scope (sorry, I can't remember the model but it was in the $200 range) He waled his way through close to 6 boxes of slugs without any consistancy whatsoever. Believe me this is not his typical shooting. 5 shot groups were moving by as much as 7 or 8 inches. Finally, he had to put the old scope with the rotating reticle back on and finished out the season with that. By the way he wound up taking a nice 10 point buck at 80 yards.

My only thought is that they must have some pretty wild clearances between parts and are counting on adhesives to hold some of these components in place. Or perhaps what ever retains the components has the ability to come loose. However, like I said at the outset, I don't have a clue how reticles could start rotating, or groups wander wildly from one set to another. By the way, we did check the mounting tightness on both scopes.

So, my question is, what features of internal construction could be possibly related to either of these malfunctions? Also, do internal component mounting techniques vary from cheaper scopes to more expensive scopes? In other words, what kind of precautions can a consumer take in his scope selections to ensure that they don't encounter these kinds of failures?

Doc

[Doc]

So, I guess my questions about scope internals and their failure modes must have been a pretty good one since nobody seems to have a whole lot of answers. I suppose that is pretty understandable. After all, how many people spend time pulling scopes apart?........lol.

Come to think of it, I do have an old fogged-up Bushnell Banner. Maybe I will try to get inside of it and see just how all those components are held in. Maybe I can answer some of my own questions.

Doc

[wtnhunt]

I honestly do not know Doc, and yes it is a good question.

I am pretty sure that there is a member here who could answer, might just have to be a bit patient as some members do not get in here as regularly as some of us.

[johnf]

I've only had 2 problems with scopes. One was a tasco world class and the cross-hairs jumped on it on every other shot. I didn't figure that out until I had gone through 3 boxes trying to sight it in. I got it set on a bench and put a bore sight on it. You could tap the scope with your finger and it would jump 4-5 inches every time. Also when adjusting it up it would go up and right down was left and down. Right to left adjustments seemed to work right. But it would still jump if it got bumped.

The other was my Horton 4X scope on my X-bow fogs up pretty bad.

[Doc]

I know that many of the cheaper, light-duty scopes that are designed for .22 rifles and such, have warnings that they are not meant to be used on shotguns and heavy caliber rifles. It's kind of like saying that "our component retention designs are so bad that repeated shocks heavier than .22 recoil will cause this scope to fall apart". This is what makes me curious as to what techniques are used in component retention inside these scopes. Another question is do these techniques vary from one manufacturer to another or one price class of scope to another.

I just hate knowing so little about the construction of something that I pay so darn much money for. But manufacturers never seem to talk about such things. I guess I have seen enough of these various kinds of failures that I feel justified in wondering how to head off the potential for buying one of these scopes with flawed designs, without just mindlessly throwing money at it.

Doc

[Dubie]

Well, I don't know much about rifle scopes, as I've never seen one apart, and googling didn't turn up any plans or cut-aways. However, when I was in highschool, I used to build telescopes of various design from this kit I got for christmas. Its was pretty much just various combinations of lenses, and arpitures, held in place by rings and ridges. From what I know from that, I can assume your cross-hairs are built into the arpiture, or secured directly infront or behind. In order to adjust the zero, this arpiture would have to move left/right and up/down. I've never seen the system, but its probably done with a screw and rail system of some kind. If its not holding a zero, its probably because one of those screws or rails became broken or loose. How to avoid this? Well, I can't tell you. Just like everything else in life, there is quality parts and junk parts. It could probably be repaired, but depending on the quality of scope, it just might cost as much to fix as buy a new scope.

Warning!: I'm making alot of assumptions based on little knowledge thats over a decade old. I just might be talking out my backside.

[johnf]

I think asking the scope manufacturers how they make a better scope would be like asking toyota why their cars run longer than others. I don't really thing you would get a straight answer other than "our tolerances are tighter", "our parts are better" or "we build them to a higher standard."

Don't think you would get a specific answer.

[Doc]

I spent a few years back in the early part of my career designing optical instruments at Bausch & Lomb. This was a long-long time ago.....ha-ha. While I never worked on their rifle scopes, I did work on instruments that mounted and contained a lot of optical components. The normal method of retention was a very good slip fit between the lense and the shouldered hole that it was mounted in, and then a locking threaded ring. That was back in the mid 60's, and I'm sure that in this age of squeezing every last penny out of manufacturing costs, that method is probably totally out of date. My thought is that today they probably rely more on chemical fastening (adhesives) than they do on mechanical fastening, but I don't know. If that is the case, it wouldn't surprise me if occasionally a chemical bond fails. The impact loading due to recoil would probably be the reason for such failures. However this is all guessing on my part since I have never looked inside a scope.

Doc

[PA_RIDGE_RUNNER]

Maybe I am the only really inquisitive mind here. I had an old scope that was litteraly junk. I had never seen the inside of a rifle scope. I took this scope apart and did learn a bit about how a scope works. First of all there is a tube within a tube the inner tube has lenses and the reticle inside it. As I recall the inner tube was secured at the rear. About half way up that inner tube there was 3 posts. These posts were attached to the outer tube. The post on top was for vertical adjustment and moved up and down pushing the inner tube. The other post was the horizontal post at the 3 oclock position. This moved the inner tube back and forth. The third post was a spring loaded plunger type of post at the 7 oclock position. This post being spring loaded exerted pressure to hold the inner tube against the other two. This was the main problem with this scope as the spring was stuck and would not move on its own. Broken springs can be a source of scope problems too. I remember reading of one style of scope where this post at the 7 oclock position is a solid post but has an external adjustment that eliminates the spring but would be a bit more to remember to retighten or loosen before making adjustments.

[Dubie]

Now that makes perfect sense, and sounds sturdier then my adjustable arpature theory....

[Doc]

PA_RIDGE_RUNNER-

That is just fascinating! I never would have even guessed that kind of internal arrangement. Now I am wondering if that is generally the way all scope internals are arranged. On the scope that you pulled apart, was that a fixed power scope? What make was it?

Whenever I get a spare few minutes, I'm still going to try to pull my old fogged up Bushnell Banner apart and see what makes it tick. Hopefully, they haven't arranged any impossible dis-assembly techniques.

Doc

[PA_RIDGE_RUNNER]

Doc when I did that it was many moons ago. I believe it was a fixed power scope that my dad got somewhere. It was not a brand name scope that I recall. If that Bushnell banner is no longer under any kind of warrenty go for it. Look at it this way the person or persons that put that scope together in the first place were not PHDs so just go at it slowly and carefully. When I did it many years ago I was absolutely intrigued at how a scope works, and just think after you are done you can just throw the parts in the trash. Let us know how a more modern scope functions inside.

[LETMGROW]

About a year ago I sent a Bushnell Banner scope back to the factory [ actually the warranty center ] I got a new scope in return. It cost me nothing as Bushnell even paid me for the shipping out. I'd contact them before you destroy that scope.

At one time Simmons had some pretty good illustrations on their website showing the construction of their scopes. I don't know if they are still there but you might research it. I think I read an article in one of my Gun Digests about scope building. I'll try to check it out. I have over 60 years of GD so it may take a while.

Lynn