Rifle Scopes another EREK question

[gknittel]

Hello guys, I need some help to figure out exactly how the EREK knob works. I've read all the posts about this and watched all the USO and youtube videos but I can't fully understand the thing...

Is it true that using this knob I will be able to zero at 100 yards and end up with about 8.5 mils for longer shots?

If this is true, how is that possible?

The center screw moves the reticle and the knob itself moves the erector tube? Is this correct?

Is the reticle moving separately from the erector tube?

Any help would be appreciated...

Thanks!!

 

[gszeto99]

Re: another EREK question

Well the way I understand how mine works on my ST-10 is the knob does bottom out independent of the erector tube bottoming out. This allows you to set up an unofficial zero stop, by bottoming out your EREK knob and adjusting your center screw which directly adjusts your erector to whatever "zero" you want (100y zero, 300y zero, 800y zero).

Now of course if you have such a bad barrel droop or a really bad mount problem where you have used up most of your adjustment to "zero" then you may not have the 8.5 Mil of additional adjustment available to you after you zero. Remember the erector tube has a LOT of adjustment range in it but still only has a finite amount of adjustment since it sits inside the scope tube.

Hope this helps

 

[gknittel]

Re: another EREK question

gszeto99 thanks for your reply...

Let me see if I understand: the reticle is attached to the erector tube and only moves when I turn the knob or the center screw... right? Meaning I can't move the reticle independent of the erector tube... right?

Now, if I mount the scope on a .22 rifle (much more drop on 100 yards than a larger caliber like a .308Win) I will end up with less than 8.5MILS of adjustment... right?

Am I understanding?

Thanks!!

 

[CSTactical]

Re: another EREK question

I talk about the EREK Knob in this article:

USO 3.2-17x ERGO

Hope it helps,

Mike @ CST

 

[JBW3]

Re: another EREK question

The reticle IS attached to the erector, moving the two together is what changes the POA/POI.

Think of a tube within a tube, this is your scope body(outer), and the erector(inner). The higher vertically you go with the erector tube inside the main tube, the firther the distance of your shot.

Depending on what model scope you have, tube diameter and magnification, this will determine how much total MOA travel you have available for use.

The knobs are set up so that you can get the maximum amount of travel out of the scope, but there are phantom clicks depending on how it is set up. These are the clicks that you feel at the top end of your travel after the erector stops moving. This happens when the erector travels all the way until it hits the inside of the tube/body.

Take as an example the 17X SN-3, with a 30mm tube you can get about 85 total MOA of travel out of the scope. So from the optical and mechanical center(when the erector is perfectly centered in the body), you will have 42.5 up, and 42.5 down.

If you mount this scope on a rifle that has a 20 MOA base, then you are taking away the 42.5 MOA down, now you only have 22.5 down, which translates to 62.5 MOA up travel. If your rifle/caliber allows for the exact center of the scope to be your 100 yrd zero, all of those numbers are good.

If you mount that scope with a 20 MOA base on a .45ACP, your 100 trd zero will not be the same as it would with a .308WIN.

If you are having any troubles getting this scope zeroed we would be glad to help you if you shoot us a call or email.
Cheers,
John III

 

[Lindy]

Re: another EREK question

Here's an article with some nice diagrams of the inner works of a rifle scope:

http://www.shootingvoodoo.com/index.php/articles/anatomy_of_a_tactical_bolt_action_rifle__the_rif/

 

[Trigger Monkey]

Re: another EREK question

To help illustrate John's post take a look at these articles I wrote:

The Riflescope

Rings and Base

Damn Lindy, you beat me by seconds with my own material lol.

 

[Lindy]

Re: another EREK question

Beat ya!

 

[JBW3]

Re: another EREK question

Trigger, the old man (Sorry Lindy) got ya on that one by 15 seconds!!! Good post guys!
John III

 

[gknittel]

Re: another EREK question

Hey, thanks all for answering!!

Mike: I already read your article. It's great, but still can't understand some things.

I mean... I know how to zero the scope, but I'm just having a bad time trying to figure out how the EREK works and what is it for and what makes it different from another knob. What keeps me confused is that I read in USO website that this knob simulates a down angle base on flat-top rifles. I just can't understand why. From my standpoint:

If I'm using an SN3 + 20MOA base, I've about 62 moa up travel... from there I start moving the center screw until the scope is zeroed at 100 yrds with a given caliber... after that, I will end up with (for example) 70 MOA of up travel and this new amount of MOA is what matters (the AVAILABLE CLICKS). This is like in any other scope.
Now, if I mount this same SN3 on the same rifle but with a <span style="text-decoration: underline">0MOA base</span>, then I've about 42MOA up travel. Again, from there I zero the scope at 100 yards and I end up with 50 MOA of up travel.
So, I don't understand what is the meaning of the sentence in USO website: "can be repositioned on the erector screw to simulate a down angle base".
The base is what allows me to have more available clicks for longer shots.

From my point of view, this is the same as with any other riflescope. Except that I've the advantage of having a "pseudo" zero-stop.

John, I understand all you write... but technically I get lost here:
"The knobs are set up so that you can get the maximum amount of travel out of the scope, but there are phantom clicks depending on how it is set up. These are the clicks that you feel at the top end of your travel after the erector stops moving. This happens when the erector travels all the way until it hits the inside of the tube/body."

Thanks everyone!!

John, I didn't write an email because I didn't want to bother you with this... it's just a doubt and since I haven't found the answer on all the posts I read, I thought it would be nice to log it here as a way to add more info about the EREK. Thanks for your patience..

 

[gszeto99]

Re: another EREK question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gknittel</div><div class="ubbcode-body">gszeto99 thanks for your reply...

Let me see if I understand: the reticle is attached to the erector tube and only moves when I turn the knob or the center screw... right? Meaning I can't move the reticle independent of the erector tube... right?
</div></div>

This part is correct. Reticle is fixed within your erector tube. Moving erector tube moves sight picture in relation to reticle.


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gknittel</div><div class="ubbcode-body">
Now, if I mount the scope on a .22 rifle (much more drop on 100 yards than a larger caliber like a .308Win) I will end up with less than 8.5MILS of adjustment... right?

Am I understanding?

Thanks!! </div></div>

Assuming it's a perfect world and barrel droop does not exist meaning both the 22lr and 308 rifles have barrels that point exaclty parallel to the scope base for example, then on a traditional scope if you zero your 308 rifle and have 8.5MILS of adjustment after zero, you will have less than 8.5MILS of adjustment after you zero with the same scope on a .22lr because the .22lr round will drop more than the 308 round at 100y. Looking at a simple traditional scope with this perfect scenario then yes what you are saying is also true.


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gknittel</div><div class="ubbcode-body">
From my point of view, this is the same as with any other riflescope. Except that I've the advantage of having a "pseudo" zero-stop.
</div></div>

Quite true actually. If you have your EREK and erector tube in-line with each other ("bottom out" EREK and "bottom out" erector tube at exactly same time) then your EREK knob would work exactly the same as any traditional scope knob.


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gknittel</div><div class="ubbcode-body">
So, I don't understand what is the meaning of the sentence in USO website: "can be repositioned on the erector screw to simulate a down angle base".
</div></div>

I love my US Optics scope and the company but to me this is just a marketing statement. I really did not understand it either but now I know what they are saying. My EREK is a double turn 45MOA turret. My ST-10 scope's erector has 100MOA of adjustment. I can "reposition" my 45MOA worth of adjustment somewhere within my 100MOA of total scope adjustment when I setup the EREK and zero the rifle.



<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gknittel</div><div class="ubbcode-body">
The base is what allows me to have more available clicks for longer shots.
</div></div>


Exactly right!!

 

[gknittel]

Re: another EREK question

Thanks alot gszeto99!!