Zero Retention: Static vs Active Erector Use... Formidilosus, your experience?

[OutdoorAg]

A scope that retains its zero during active use of the erector (dialing)...is this also a scope that is MORE likely to retain zero after no use (static) of the erector system?

Meaning...Can I expect a scope with a better RTZ track record to also be a better "its still where I left it" scope? Are the 2 related?

@Formidilosus

 

[Wrench]

If it doesn't RTZ.....that's the end of the test.

Hard to evaluate if it is not able to get to step one.

 

[Formidilosus]

Meaning...Can I expect a scope with a better RTZ track record to also be a better "its still where I left it" scope? Are the 2 related?

@Formidilosus

In general, yes. There are exceptions it seems with some old scopes, but in general- the better a scope is a retaining zero; the better it is at retaining zero. But I wouldn’t really say the RTZ is the best indicator of that. The best indicator of a scopes ability to maintain a static zero are the drop portions, then high round count tracking of zero.

 

[josef]

What do you believe is failing inside the scope during your drop tests?

 

[Formidilosus]

What do you believe is failing inside the scope during your drop tests?

I do not know.

 

[BBob]

What do you believe is failing inside the scope during your drop tests?

My guess: They all have erector/zoom mechanisms that pivot (7) at or near the eyepiece on the back end. There is a spring or springs (9) opposing the turrets (8) on the front end. It wouldn't take much displacement at all at either end to knock POI out when dropped if they are bounced out of place and do not return to the same place after they are dropped. Others in the benchrest world that have modified scopes have also found loose lenses that caused POI changes.

Simplified drawing:

 

[josef]

Would that just be a zero shift or would groups open up too?

 

[BBob]

Would that just be a zero shift or would groups open up too?

If a scope won't hold zero group size is likely to be larger and of course there is also zero shift so quite likely both. In the BR world if you have a scope that will not hold zero, increased group size is quickly noticeable when swapping scopes and one isn't holding zero. With a hunting rifle you may not notice it much if the scope isn't too bad at zero retention. I have multiple scope checkers where two scopes are mounted side by side. One scope can be a frozen (erector mechanism is frozen in place) or a known good scope. You shoot them side by side and look for a displacement in the scope to be tested. Occasionally you'll find rings and not the scope that won't hold zero for whatever reason. Not as tough or rough as drop testing scopes though

 

[josef]

I do not know.

Are you seeing group shift or groups opening up?

 

[josef]

If a scope won't hold zero group size is likely to be larger and of course there is also zero shift so quite likely both. In the BR world if you have a scope that will not hold zero, increased group size is quickly noticeable when swapping scopes and one isn't holding zero. With a hunting rifle you may not notice it much if the scope isn't too bad at zero retention. I have multiple scope checkers where two scopes are mounted side by side. One scope can be a frozen (erector mechanism is frozen in place) or a known good scope. You shoot them side by side and look for a displacement in the scope to be tested. Occasionally you'll find rings and not the scope that won't hold zero for whatever reason. Not as tough or rough as drop testing scopes though

That sounds interesting. Are you able to post photos of one of these scope checkers? Do you have them for work or just play?

 

[BBob]

For testing personal scopes. One is dedicated to Picatinny rails/rings and the other for Davidson rails with an option to add a Davidson to Picatinny rail adapter to one side. This testing has been going on for a really long time in the BR world. Part of the reason why we have Deon Optical/March scopes on the table is from the drive from short range BR to find a scope that would hold zero. Another interesting thing that was fairly common for awhile in BR was fixed/frozen scopes with external adjustments. They made a full circle back because nothing would hold zero. March built a scope that satisfied and most drifted back to internally adjustable. I don’t know how they would do in drop tests (probably not well) but for target use the Vortex Golden Eagle is very good about holding zero on a BR rifle. They are very common in long range BR and F class. There are others out there that test well on the scope checkers and are known to hold zero in competition.

 

[BBob]

Frozen Leupold Comp scope and a Gene Bukys TSI external mount. Gunsmith Bob Brackney made a similar unit.

 

[ChrisAU]

So the gist at the time was “no one will make a scope that tracks so we’ll spend exorbitant amounts of time and money to rig something up”? That sucks.

 

[BBob]

So the gist at the time was “no one will make a scope that tracks so we’ll spend exorbitant amounts of time and money to rig something up”? That sucks.

Pretty much. A short range benchrester by the name of Lou Murdica put up big bucks to get Deon Optical to build the first March scope to specs that would satisfy short range BR zero retention. I don’t remember the exact details anymore but that might have actually been the start of March itself. The frozen scope thing was quite a little industry in itself for awhile.

So here we are in the hunting world demanding close to what the BR guys chased long ago (and are still chasing) today. I think our requirements are a little tougher asking for zero retention with larger impacts but if Nightforce can do it others can if they want.

 

[Formidilosus]

So here we are in the hunting world demanding close to what the BR guys chased long ago (and are still chasing) today. I think our requirements are a little tougher asking for zero retention with larger impacts but if Nightforce can do it others can if they want.

Similar maybe. But a hundredth MOA reticle shift shot to shot will not effect hit rates at all in the field. It matters for SR BR, and it shouldn’t happen at all, but even a tenth moa shift between shots doesn’t effect anything for field rifles. If a gun will keep all shots in a 1.5moa dot at 100y no matter what, the rifles precision isn’t the problem on animals even out to quite long ranges.

 

[BBob]

With a hunting rifle you may not notice it much if the scope isn't too bad at zero retention.

But a hundredth MOA reticle shift shot to shot will not effect hit rates at all in the field.

Yup, pretty much said that already

 

[Formidilosus]

Yup, pretty much said that already

I know. I wanted to clarify because I have went through two cycles in the past of guys losing their minds about shot to shot reticle jump, and I’m already getting asked about it now. These were all field shooters with 1-1.5 moa rifles losing their minds due to a couple hundredths moa reticle jump. This lead to scope checkers being bought and used on all scopes- including red dots, and some putting BR scopes on LR field rifles with disastrous results.

People latch onto things that are inconsequential and neglect the things that actually matter. I appreciate the info, I just wanted to make it clear to those asking me that for the most part this has no effect on field use.