Rifle Scopes Scope Repeatability - the mechanics

[Dsparil]

I'm definitely not an engineer by any means. I was curious as to exactly what contributes to a scope's repeatability?


I mean what efforts do higher end manufacturers take that make their scopes more repeatable than cheaper scopes?


i.e. something like Falcon Optics vs Nightforce I guess would be a good way of putting it. FYI I currently run nightforce and love it. Just curious about the mechanics.

 

[RTH1800]

Re: Scope Repeatability - the mechanics

Like anything else, it comes down to design, material and precision mfg. And the top end scopes do excell at it. When you pick up a S&B or USO and turn the dial, you know you have fine machinery in your hands.

 

[strat81]

Re: Scope Repeatability - the mechanics

I have heard some of the cheap units have erectors made from plastic, rather than metal. Can anyone confirm that?

 

[redneckbmxer24]

Re: Scope Repeatability - the mechanics

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rth1800</div><div class="ubbcode-body">Like anything else, it comes down to design, material and precision mfg. And the top end scopes do excell at it. When you pick up a S&B or USO and turn the dial, you know you have fine machinery in your hands. </div></div>

Perfectly said. It's all about the quality of materials and workmanship that goes into it.

Cheap scopes are cheap because the materials and labor is cheap. You can't have a $200 scope equal that of $2000 one, a lot of things have to give.

 

[turbo54]

Re: Scope Repeatability - the mechanics

Ultimately, the riflescope is a tube inside a tube.

The inner tube is the erector housing, and it is supported by springs.

A vertical screw (your elevation turret) pushes down on the erector housing (acting against the spring), angling it for elevation adjustment.

A horizontal screw (your windage turret) pushes sideways against the erector housing (against a spring), angling it for windage adjustment.

The backlash between the male/female threads for turret adjustments are crucial to good tracking. If they wear, tracking and return to zero will be effected. The springs must absolutely guarantee the erector housing is properly seated against the turret screws, or else calibration will be off.

Awesome scopes choose materials and machining practices and sometimes extra parts that provide zero backlash, and very low wear.

This is an extremely oversimplified explanation, but I hope it gives you the idea.

 

[Ledzep]

Re: Scope Repeatability - the mechanics

As was stated above, the elevation and windage adjustments are more or less screws.

Take a nut and bolt. Screw the nut halfway down the bolt. Then, without rotating the nut or bolt, push back and forth on the nut. You will probably feel it move a little bit. That is called "backlash". When that exists in an elevation/windage turret, there is a greatly increased chance that the scope won't track well.

For example, you may move the turret 5 clicks and not have any change in impact, and from there on, it tracks correctly. Then you try to go back the other direction, and get 5 clicks of nothing, then it starts tracking correctly again. For this reason, some cheaper scopes are better off moving it 5 MOA left, then 2 MOA right to achieve 3 MOA left, instead of simply going 3 MOA left. Clear indicator of backlash. Another one is having to shoot the rifle 3-5 times to get it to "settle in", or tap turrets (I am very skeptical of Acogs for this reason).

Also, any inconsistency in the thread geometry will cause issues where the clicks will give different values. This comes down to quality machinery and operators of machinery.

If there are any rough spots on anything that touch each other inside the scope, you have the chance of things binding up a bit and skewing adjustments or having inconsistent adjustments.

Improper design or poor assembly can cause clicks that aren't true 1/4 MOA or 1/10 Mil, or reticles that don't actually read to the correct scale.

Basically, it comes down to the quality of design, materials, the machining/manufacturing, and the fitting of parts. You're paying for higher quality materials (Glass more than anything) and labor.