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Question about a scope's erector tube and spring

Printed From: OpticsTalk by SWFA, Inc.
Category: Scopes
Forum Name: Rifle Scopes
Forum Description: Centerfire long gun scopes
URL: http://www.opticstalk.com/forum_posts.asp?TID=44757
Printed Date: September/18/2018 at 20:54
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com


Topic: Question about a scope's erector tube and spring
Posted By: tpcollins
Subject: Question about a scope's erector tube and spring
Date Posted: March/28/2018 at 09:51
A typical scope should have a turret at 12 o'clock and 3 o'clock. A spring is located at about 7:30.  If the windage turret for example is nearly maxed out going in one direction, can it influence the elevation turret as well. 

Or is the bottom of the turret large enough to keep it on plane and from sliding off the round erector? I had Vortex tell me once that if the elevation was maxed for example, then erector tube could bump the inside of the scope tube and affect the windage as well - make sense I guess.

Just wondering which would be most likely to change POI - the round erector sliding off the bottom of the turret or the erector tube bumping the inside of the scope tube?  It might make a difference whether it's a $100 scope or a $1000 one .  Thanks.







Replies:
Posted By: koshkin
Date Posted: March/28/2018 at 10:28
The question is too generic since there are multiple ways of building this system.  Different scopes have difference spring arrangements.  The means of how turret stems contact the tube vary.  The overall amount of adjustment that the turrets can have is often guardbanded with stops put in that prevent excessive pressure on the erector tube, etc.

With PRB, you have to be really careful with how you interpret the optics info there.  It is often misleading due to being either over simplified or just wrong. 

If you plan to spin the turrets a lot, none of the $100 scopes will do the trick.  The erector tube is not supposed to bump the inside of the maintube since there should be a limiter in action prior to that.  On cheap scopes it might do something like that, but not on any decent ones.

Being at the very end of vertical adjustment can effect horizontal adjustment and vice versa, but you have to keep in mind that there are other effects at the end of the adjustment.  For example, for many scopes, if you adjust that far, you need to re-adjust the parallax.

ILya


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Posted By: sambarman338
Date Posted: July/03/2018 at 07:53
As koshkin says, there are various spring arrangements used to hold the erector tube against the turret screws. Most use a flat spring at 7.30 but (in investigating the decadence of image-movement for a book on scopes) I have come to believe friction between the tubes at extremes of adjustment is likely to cause erratic tracking and even spring breakage. This may be the main reason Swarovski  uses a little knob at the end of their Z3 springs and four coil springs at the rear of the erector tube on Z5 And Z6 models.

It may also be the reason behind Leupold's copper beryllium springs, assuming the copper adds some greasiness that helps them slide against the opposing surface.

I used to think the initial whacking of the erector tube against the bottom of the scope under recoil was the main danger to the mechanism but now think the second recoil impulse (the deceleration of the rifle against the shooter's shoulder) may be worse. Though the second impulse is less violent than the rising of the rifle at the shot, it sees the erector tube returning from the matrix-like smoothness of the outer barrel to be smashed against the elevation screw. When extreme windage has been employed (to make up for poor mounts or mounting) it may be scraped past the lateral screw, removing or denting metal on the side as well.


Posted By: tpcollins
Date Posted: July/03/2018 at 19:09
Since all I ever saw about the erector, spring, and turrets is posted in my initial post, I couldn't figure how that would work. And then a contact I've dealt with at Vortex sent me this illustration and then I understood how turning the turret out dropped the reticle down  - the teeter totter affect!  







Posted By: Urimaginaryfrnd
Date Posted: July/03/2018 at 19:45
Stern Smile someone has way too much time on their hands. Use a mil dot reticle and simply hold over - problem solved.  Plan B work with the scope you have so you know what it will do. 


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"Always do the right thing, just because it is the right thing to do".
Bobby Paul Doherty
Texas Ranger


Posted By: tpcollins
Date Posted: July/03/2018 at 21:15
Originally posted by Urimaginaryfrnd Urimaginaryfrnd wrote:

Stern Smile someone has way too much time on their hands. Use a mil dot reticle and simply hold over - problem solved.  Plan B work with the scope you have so you know what it will do. 

I must be living rent free inside your head - just because you don't know or care how something works doesn't mean everyone else is the same. I like understanding how things work - after all, it is MY time we're talking about.

Do you offer sarcasm to everyone on this forum or just me?   Why even post if you don't have anything positive to offer?


Posted By: sambarman338
Date Posted: July/03/2018 at 22:13
The Vortex illustration is interesting but I'm not sure its application is universal. I know that when I want to lift bullet impact with my old reticle-movement scopes,  I need to take the reticle lower in the field. To make that happen on an old Nickel 4x36 I have, the turret screw needs to be turned clockwise (in?). While that seems intuitive, the existence of the erector set and ocular lenses between the reticle and your eye obviously complicate matters. If the reticle is in fact upside-down in the tube, as I have seen with early Pecar scopes, it must be also invert the logic of my understanding.

Strangely, the replaceable reticle Pecar supplied for their later, image-movement Champion line sat upright in the tube, which makes me wonder how it all works - never mind how the reticle, detached from the erector tube, managed to be constantly centred.


Posted By: sambarman338
Date Posted: July/03/2018 at 22:28
Originally posted by Urimaginaryfrnd Urimaginaryfrnd wrote:

Stern Smile someone has way too much time on their hands. Use a mil dot reticle and simply hold over - problem solved.  Plan B work with the scope you have so you know what it will do. 

While I agree that using stadia, mil dots etc are a better idea than cranking the knobs at every shot, trying to understand how scope adjustment works is not a bad idea. If more people cared, maybe the smoke and mirrors of constantly centred reticles would have been seen for the BS it is 60 years ago and been left behind like white-wall tyres and fins on cars.

One thing I would not like about clicking to make that distant shot, is the possibility I might forget to wind it back. At least if you did that with old reticle-movement scopes, the reticle left low in the field would remind you something needed to be done.





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