Scopes inner workings
- Thread starter sully7mm
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An erector tube is what is moving inside the scope. I don't know about all of them, but most work in the same fashion but are set up a little differently. Some have the erector in the front, while others its in the back. It's really quite a simple mechanism, where one end of the tube is attached to the turrets and the other has some kind of a joint where the tube can pivot. Some sort of springs oppose the turrets to keep the erector from moving around and changing POA,theoretically).
I have to also ask about the mechanical movement. It seems to be a very simple straight forward mechanical thing. What causes this simple setup to fail or not move as it should?
I just sent a scope back for the second time. The groups opened up to 2+ inches. Make an adjustment L or R 1 or 2 clicks the POI is as much as 3-5 inches out. After a couple of rds it would settle back to where it should be and shoot a large group.
Bought a new scope because I was so PO'd,same brand different power, I own a few of them, do not ask me why I bought another),if this scope comes back and does not preform it will be the last ever). I'm back to 5 shots touching good POI everytime,cold & clean needs 2 foulers) cold or warm after foulers POI is accetable. Typically shoot out to 300 yds on vermin.
How precise should the adjustments be on the box test?
I just sent a scope back for the second time. The groups opened up to 2+ inches. Make an adjustment L or R 1 or 2 clicks the POI is as much as 3-5 inches out. After a couple of rds it would settle back to where it should be and shoot a large group.
Bought a new scope because I was so PO'd,same brand different power, I own a few of them, do not ask me why I bought another),if this scope comes back and does not preform it will be the last ever). I'm back to 5 shots touching good POI everytime,cold & clean needs 2 foulers) cold or warm after foulers POI is accetable. Typically shoot out to 300 yds on vermin.
How precise should the adjustments be on the box test?
Fred Bohl
Gold $$ Contributor
Harvey
By way of background, I do a lot of scope mounting, re-mounting, bore sighting and trouble shooting at our club,150+ per year) with 8 of 10 being on hunting rigs. The most common cause of adjustment failures is the user driving the erector tube to one or both of the extremes which results in distortion of the spring,s) that hold the erector tube in place and/or damage to the threads of the adjustment shafts,very fine pitch and not very strong threads!). The next most common failure mode is due to impacts,dropping from tree stands or collision with trees and pickup beds) which tend to also damage the erector tube springs and loosen internal parts.
Another issue is selection of scopes too fragile for the firearm. Many scopes are usable on small to medium caliber hunting rigs. However, the heavy bullet max load big caliber magnum rigs need much more durable scopes. The failure symptom most common is an axially displaced or loose erector tube or reticule due to recoil.
As to "How precise should the adjustments be on the box test?", I expect most scopes with click adjustments to track very accurately within the range of +or- 8 MOA of optical center. As you get further off center the linearity gets worse. If you have used more than 8 MOA of adjustment to achieve sight-in alignment, it is not reasonable to expect an accurate box test in any but the finest scopes.
We tend to have very unrealistic expectations of our scopes. Remind yourself that these are assemblies of glass, aluminum, brass and elastomeric seals,O-rings) that all have different thermal expansion rates very fine tolerances and tiny but necessary clearances,to allow even small movements). Then we expect them last forever and to hold zero over wide temperature, humidity and pressure changes also after rough air, road and foot transport and last but not least while being rigidly coupled to a firearm subjected to repeated detonation and recoil containment events.
By way of background, I do a lot of scope mounting, re-mounting, bore sighting and trouble shooting at our club,150+ per year) with 8 of 10 being on hunting rigs. The most common cause of adjustment failures is the user driving the erector tube to one or both of the extremes which results in distortion of the spring,s) that hold the erector tube in place and/or damage to the threads of the adjustment shafts,very fine pitch and not very strong threads!). The next most common failure mode is due to impacts,dropping from tree stands or collision with trees and pickup beds) which tend to also damage the erector tube springs and loosen internal parts.
Another issue is selection of scopes too fragile for the firearm. Many scopes are usable on small to medium caliber hunting rigs. However, the heavy bullet max load big caliber magnum rigs need much more durable scopes. The failure symptom most common is an axially displaced or loose erector tube or reticule due to recoil.
As to "How precise should the adjustments be on the box test?", I expect most scopes with click adjustments to track very accurately within the range of +or- 8 MOA of optical center. As you get further off center the linearity gets worse. If you have used more than 8 MOA of adjustment to achieve sight-in alignment, it is not reasonable to expect an accurate box test in any but the finest scopes.
We tend to have very unrealistic expectations of our scopes. Remind yourself that these are assemblies of glass, aluminum, brass and elastomeric seals,O-rings) that all have different thermal expansion rates very fine tolerances and tiny but necessary clearances,to allow even small movements). Then we expect them last forever and to hold zero over wide temperature, humidity and pressure changes also after rough air, road and foot transport and last but not least while being rigidly coupled to a firearm subjected to repeated detonation and recoil containment events.
Thanks Fred that is a great explaination.
I just have no inkling why this scope has Gremlins in it.
It has drove me nuts.
It is a high end scope. I'm just not willing to throw the maker under the bus. I have 2 scopes that are 30+ years old and still preform flawlessly.
I just have no inkling why this scope has Gremlins in it.
It has drove me nuts.
It is a high end scope. I'm just not willing to throw the maker under the bus. I have 2 scopes that are 30+ years old and still preform flawlessly.
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