What actually MOVES when a scope gets bumped?

[Bladebum]

Ok, this topic has been bothering me for a long time and I have never heard an actual logical answer. If a scope gets "bumped" or takes a fall, what is it that actually shifts in the scope that makes it lose it zero or poi?

On scopes of old days, they were not nearly the quality we have to choose from today. You had wire reticles on most and hardware that was not intended for heavy use. But things have changed substantially, and scopes are built extremely rugged able to hold up to the harshest environments and highest recoiling guns. Also with the very sturdy mounting systems today, it would be very difficult to get a scope to move around in those.

Aside from actually taking a hard whack on a rock or something and bending the tube of the scope or breaking internals completely, what could possibly move on a modern scope? Are the days of getting "bumped" off a thing of the past? I have never had a scope be off zero in all my hunting ventures of bouncing around mountains and trucks, and have the hardest time understanding which parts can move from just light bumping around.

 

[pan60]

great question.
aside from the old days of wire reticules i have wundered if these ( particurly etched glass as i guess some are still wire? ) modern scopes will change POI?
i was at a buddies the otherday and he made some tweeks and would take his pocket knife and tap tap, i ask what he was doing and he said it help the scope setle in LOL i told he i real could nit see that being needed but he insisted it was the thing to do.

 

[Spinach]

In the early days of using MTC scopes, whenever there was a problem the response was, hit it with a shoe.
Surprisingly it worked.
My scopes get abused, all thanks to scope sellers instructions.

 

[Farmplinker2]

In the old days, and still some today, machining might not be as precise. So bumps could bounce the adjustment surfaces. Say, 10 teeth might be machined lower than the rest. So your scope might drift that much over a long time. Also, don't forget about the possibility of screws loosening due to vibration.

 

[MountainSportAirguns]

Believe it or not scopes can take a pretty good beating, it's usually the gun that loses poi. This could be from not mounting the scope correctly and something coming loose. Typically it's other components, specifically the barrel system that might be the culprit to losing poi. A good way to test a scope is to rock the turrets side to side and try twisting them between clicks to check for play...a quality scope should have zero play.

 

[Bladebum]

So it seems that most here would agree, on a modern day scope there really is no reason to assume the scope can bump off short of being actually damaged.

This question for me rekindled interest on an elk hunt i went on with my dad about a month ago. We stopped off somewhere in Nevada to check zeros on some rifles. As mentioned above, the old "tap it a few times to settle the turrets" popped up , and it made me laugh...my dad is not too familiar with a target turret scope and I told him there is zero reason to tap a scope thats meant for dialing...by nature that would be a HUGE problem if the turrets needed to "settle" every time you dial. It led to a good long conversation on the rest of our 9 hour drive, to which the conclusion was basically, there is zero reason for a scope to shift or bump off.

Now, I do know that temp swings can affect things both on scopes and guns. Quite possibly, what used to shift poi on equipment of old was in fact that. As Dana mentioned, even barrels shifting slightly could be suspect. Now, most people shooting centerfires needing to hit the vitals of a deer or elk would never see these micro shifts(somewhere) , but as airgunners, a 1" shift at 75 yards is a wound or miss on quary.

 

[Madeintheuk]

Most of the scope bumps I’ve witnessed have caused poi issues from mounting hardware. The “cheap” rings everyone seems to use when buying nice scopes are the weak link. Scopes are usually pretty solid.

 

[Solo1]

A lot depends on conditions too. I have a $250 leepers scope that if its real cold and i adjust 2 clicks windage and hurry up and shoot it moves about 1 click by the time i shoot the 2 nd or 3 rd shot its moved 2. Don’t know if its thick lube or just tight from cold but it does it

 

[Hoppalong Doc]

A lot depends on conditions too. I have a $250 leepers scope that if its real cold and i adjust 2 clicks windage and hurry up and shoot it moves about 1 click by the time i shoot the 2 nd or 3 rd shot its moved 2. Don’t know if its thick lube or just tight from cold but it does it

Solo, I'm trying to figure out just what could be causing your poi jump. I've got a $400 scope on my TX200. While we were traveling through Texas this summer, the ambient temperatures often exceeded 120 degrees. My Hawke scope needed re-zeroing once we left the heat of Texas and settled in to shoot up at another sons' home near Seattle where the temperatures rarely reached 75 degrees. My point is, ambient temperature changes do indeed change the zero on our scopes. Our scopes advertise that they are purged with nitrogen. . . could this be influencing our scopes? I know that altitude affects the oxygen in our air. Could the heat cause the nitrogen pressures to change in our scopes? My mind is just rambling on here, but I am truly curious here. Thanks for reading on here. Orv.

 

[PasadenaMike]

Believe it or not scopes can take a pretty good beating, it's usually the gun that loses poi. This could be from not mounting the scope correctly and something coming loose. Typically it's other components, specifically the barrel system that might be the culprit to losing poi. A good way to test a scope is to rock the turrets side to side and try twisting them between clicks to check for play...a quality scope should have zero play.

What he said

 

[PasadenaMike]

Solo, I'm trying to figure out just what could be causing your poi jump. I've got a $400 scope on my TX200. While we were traveling through Texas this summer, the ambient temperatures often exceeded 120 degrees. My Hawke scope needed re-zeroing once we left the heat of Texas and settled in to shoot up at another sons' home near Seattle where the temperatures rarely reached 75 degrees. My point is, ambient temperature changes do indeed change the zero on our scopes. Our scopes advertise that they are purged with nitrogen. . . could this be influencing our scopes? I know that altitude affects the oxygen in our air. Could the heat cause the nitrogen pressures to change in our scopes? My mind is just rambling on here, but I am truly curious here. Thanks for reading on here. Orv.

Scope temp is very important to monitor . I learned this in HFT . The guys actually keep a laser thermometer, they keep the scope covered…..makes a difference. I’m not serious enough to care but I know it’s a thing. Apparently heat messes with parallex which shifts poi. My guns as long as they’re hitting ground squirrels I don’t care

 

[Hoppalong Doc]

Mike: I only care enough to help me in figuring out poi shift. I really like shooting with accuracy and knowing the why helps me with the what and how. Orv

 

[PasadenaMike]

Mike: I only care enough to help me in figuring out poi shift. I really like shooting with accuracy and knowing the why helps me with the what and how. Orv

Best thing is contacting the scope manufacturer and see what they have to say.

 

[Solo1]

Well its like anything else heat makes metal gasses etc expand cold does the opposite. I’ve personally never had a scope apart but i would guess there are quite a few parts in there to get from your parallax knob to the lens it moves so think what happens if every part expands just .001” ! As for point of impact change i think thats why most higher end scopes have etched reticles not wire ones.

 

[PasadenaMike]

$4000 Sightron = no shift

 

[pan60]

$4000 Sightron = no shift

thats what i need on my 50.00 Benjamin : )

 

[PasadenaMike]

thats what i need on my 50.00 Benjamin : )

lol yeah

 

[Hoppalong Doc]

OK, now say I'm monitoring my scope temperatures most carefully. I especially keep track of the parallax whenever I'm shooting at unknown distances/elevations. What's next? Orv

 

[Farmplinker2]

thats what i need on my 50.00 Benjamin : )

If someone has a spare $2000+ scope, please mount it on a Wal-Mart special. Then post an article, "Maximizing the Crosman 760".

 

[Bladebum]

So in my line of work, I do have an understanding of nitrogen and what it's used for. They use it in many applications to purge an atmosphere of impurities, gases etc. , creating an environment that is unaffected by outside sources. In liquid form, it is colder than -300f , im not sure in gas form. From my understanding, they purge rifle scopes with it for 2 reasons, one there is no ambient air inside to move and change with temperature. And two , since there is no oxygen or other gases fogging from inside becomes very nearly impossible. Depending on how well things are purged prior to sealing would decide how dependable the shift in poi from ambient temps would be, and I suspect that is more or less the reason you pay more for higher quality scopes.

I think if there's a consensus in the input here, it's that no ones dead certain how or if a scope internals can move, but poi shifting is certainly a thing among projectile shooting devices. Mounting systems, temp affected lower end scope parallax, charged air temps and barrel bumps or shifts themselves all seem to be multi part culprits.

The topic of "my scope got bumped off" has always been a thing groing up in the firearms and hunting world. I always just accepted it as true, but in latter years have failed to see how. Scopes of old with wire reticles and not near the technology gone in as well as the mounting systems i can see where micro shifting could have happened. Now adays i just think that is mostly a thing of the past