Scope Field Eval Explanation and Standards

[Formidilosus]

This will be about the “why” of the field evaluations- specifically the drop “tests”.


Let’s have a thought experiment. Let’s say you have spotted a buck across a valley, planned and executed a stalk which when you get to the last little knob up ahead, will put you within 400-450 yards of the buck. He’s a good buck, you’re excited and in your haste you slip and fall on top of your rifle. You try to protect it, and it’s not a terrible hit, but the scope did impact the ground hard enough to make you cringe.

What do you do? How confident are you that the scope will still be zeroed? Do you leave the buck, walk back to the truck, go find a range and check zero because shooting at a deer with a potentially unzeroed rifle isn’t ethical? Or do you go ahead, finish the stalk and take a shot hoping that the rifle is still “close enough”?

Welcome to hunting situations all over the world, every single year. I do not know a single person that hunts in broken terrain, that isn’t a rank beginner that hasn’t faced similar. The reality is that no one will leave the animal- everyone will try. And most of the time, at a minimum the shot will be slightly off and very often it’s a miss or a wound.

Why is it standard practice the world over to check your zero right before a hunt? Get to deer camp- check zero. Drive across the country for your antelope hunt- check zero. Land in Africa and the first thing the PH has you do is- check zero. Why? If scopes (and rifles) are so reliable, why is it known by nearly everyone that you need to check zero before hunting even if nothing has changed since the last season or the last time you shot it? What’s worse, is very often your zero has moved a bit- it’s not exactly where it was. Critical thinking should cause intelligent people to start asking why things are moving? Why is it so known that you should check zero immediately before hunting?

The easy and obvious answer is because the vast majority of scopes don’t hold zero. We will remove rifle issues for this discussion, acknowledging that a lot of problems are exaggerated by loose action screws, and faulty mounting systems. But even when you remove the action screw and mounting variables by using a rifle that can not physically have a problem because the action is permanently bedded to the stock, and it has an integral scope base- the amount of times that the rifle loses zero is alarmingly high. Even when most say they have never had a rife lose zero, when you ask them where they are zeroed and what does the rifle group, and then immediately have them shoot they don’t hit that size target, at that range on demand- it’s always off. And then the excuses start. It’s always an “off day”, or they changed primers, or they forgot to reset the turret, etc, etc.

The human element is real, but it is not hard to learn to consistently pull a trigger without disturbing the rifle from sandbags. And, an “off day” would mean that your groups are larger, not that the center of your groups are off zero. So again acknowledging that the shooter is a source of error, why is it that when you remove the shooter source of error- the amount of times that the rifle loses zero is alarmingly high?


What do I mean by “losing zero”? I mean dead on zero. Not close, not similar, not about two inches high- I mean exactly on. If the rifle is a sub moa rifle and zeroed at 100 yards- when I shoot it, the first, and every subsequent round hits inside a sub moa dot at 100- no excuses.

How many people have shot a rifle and scope with the exact same lot# of ammunition or reloads from the exact same lot of powder, same lot of bullets, and same lot of primers for hundreds of rounds, checking the zero often and have never had a single round not hit the target exactly on zero?


The base reality is this:

If you have not done so, then you do not know that your scope holds zero. If you have done so, and you have had to make a single click to the zero a single time- your scope has lost zero. Yes there are variations in how much a scope loses zero. And how much is acceptable is up to each person, and if someone wants to say that inch or a couple inches at a hundred yards isn’t that big of a deal- well ok. But it is. Scopes are solely an aiming device used to steer bullets at targets- their base function is to do that.



In the next post I’m going to explain a partial history and the how and why of the Field Evals conducted….

 

[Formidilosus]

(Edit February 1, 2022


After speaking with Ryan, the drop eval will move to immediately after zeroing the scope. It’s the thing that matters the most, and if a scope fails that, the rest doesn’t really matter anyways. As well, the plan is that if a scope is relatively unknown as far as longevity, then it will be shot and used for 3,000 rounds to gauge its ability to function correctly in normal use)



The Evaluation:

All is conducted using rifles that have permanently bonded action to their chassis- there cannot be a shift due to the rifle/stock. Those rifles either have rails integral to the receiver, or rails permanently bonded to the receiver- there cannot be a shift due to base mounts. Any shift that is seen must come from the rings or scope itself. The rings are easy, all good picatinny rings exert a force on the rail that would physically damage the rail or scope before movement when mounted correctly- there is not a shift due to rings moving. This leaves the scope.


Full Eval:

1). Rifle is proofed with a 30-round group at 100 yards fir precision and zero. The rifles and ammunition used will be sub 1.5” for 30 rounds.

2). The proof rifle and scope go through the drop portion to prove that the rifle holds zero.

3). The new (scope being evaluated) scope is cleaned, tube degreased, rings have all oil and grease removed, scope is mounted, all screws get thread locker and torqued correctly- generally 18-20 in-lbs depending on rings.

4). Scope is mounted on rifle that was proofed and bore sighted.

5). First shot is taken at 100 yards, if on paper nine more are fired for a ten-round group. Group is checked to ensure it is within expected size- if 30 round group was 1.1”, then the ten round groups should be as well.

6). The reticle in the scope is used if it has one, or a spotter with a reticle if it doesn’t, to measure from the center of the ten-round group to the center of the aiming point. Then is adjusted.

7). A second ten round group is fired, noting of the scope adjusted exactly as it should have. Any errors are noted.

8). The target is sized based on the 30-round group. If those ten rounds all hit inside that target, then it moves on. If not, more groups are fired until it is zeroed correctly.


9). Drop evaluation. A correctly sized target is placed. On soft ground- standard grass range- a half inch padded shooting mat is placed down. The rifle is dropped once on each side (left, right, top) from 18 inches with a confirmation shot taken after each drop. Any shot that misses the sized target is noted. If it loses zero- that is a shot does not hit the sized target, then it is immediately shot on another target to check if the drop bound up the erector and if the recoil from the next round settled. If it does or does not, it is noted. Then the exact same procedure is conducted at 36 inches. Any errors noted. Then the scope/rifle is dropped three times on each side from 36”, for a total of nine drops for this portion and zero is checked. The total amount of drops from both 18” and 36” is fifteen (15).


If the scope losses zero, then the whole drop eval is repeated. If it loses zero again, then the proof scope is remounted, zeroed, and drop checked to ensure the rifle isn’t at fault. When the rifle and proof scope are proven again, the test scope is remounted, rezeroed and the drop eval repeated. If it fails the third time, it is noted and no further drop evals are conducted. Depending on use, either the scope is deemed a failure and removed from evaluating, or if still semi functional is zeroed and used for normal purposes noting when issues arrive.





10). A separate target sized correctly is used to check return to zero (RTZ). A shot is taken at the target, the elevation and windage turrets are spun for 200 mills back and forth then returned to zero. A second shot is taken, the turrets are spun 200 mils. This continues for ten times, with a total of 2,000+ mils being adjusted. The group is checked for placemat- all in the target, and size compared to baseline.

11). Live fire check of “tracking”. Two correctly sized targets are placed ten mils apart, vertically aligned. The dots are measured with the reticle as well if present. All shots will be fired aiming at the bottom target. Reticle plum is maintained throughout. A shot is fired, then the elevation is adjusted to 10 mils, second shot is fired, down 10 mils, fired, etc, etc. until ten rounds have been fired on each dot. Both groups are checked for size and placement. Any errors noted.

12). If a scope passes the initial eval, then it is mounted to standard on a proofed rifle system, is zeroed, and then carried, hunted, and shot for 3,000 rounds.




Scopes are labeled either “PASS”, “PARTIAL FAIL”, or “FAIL”.



What does that mean exactly-

PASS: In initial eval the scope adjusted and tracked within 2%, and returned to zero correctly. All groups were sized as they should, no off-call shots. All rounds from the drop test hit the group sized target- no loss of zero at all. Scope was used heavily for the 3,000 rounds without issue.

PARTIAL FAIL: In initial evaluation either the scope has more than 2% error in adjustments but was consistent, groups sizes were larger than base line, or the scope passed the 18” and 36” single drops holding zero but lost zero on the 3x3 36” drops.

FAIL: In initial evaluation the scope failed to function as an aiming device. Tracking or adjustments were more than 10% off or not consistent, it did not return to zero or failed to maintain zero on the single 18” or 36” drops.

 

[Formidilosus]

The History:

Say that you have a group of buddies. All of them shoot and hunt a lot- A lot. Ammunition expenditure per year is measured in pallets, not cases. As you shoot and hunt, you notice misses on animals and targets that should not have happened- failures. At first everyone chalks it up to “stuff happens”. But it keeps happening. Then you start noticing trends- some rifles and scopes never have problems, some are consistently causing issues. So everyone starts keeping a log of what happens. Soon it becomes obvious that through round counts and hard use that some scope and rifle options have way less issues, and a couple failures are near unheard of. Being that no one likes failures, experimentation with their own rifles and scopes start happening to see if the issues seen in general use can be replicated on a range.
Everyone talks and agrees that the most common issue is the rifle shaving to be rezeroed most of the times when checked- that is they aren’t exactly as the last time they were shot. Quickly
It’s found that different lot numbers of the same ammo have different point of impacts. So hundreds of rounds are set aside just for checking zero of the same lot for each gun. Each time a rifle loses zero, the cause is tracked down. Doesn’t the long to find that action screws get loose, or bases move, or rings let scopes slip.
Through process of elimination it’s found that a certain rifle type can not lose zero due to a permanently bonded action to “stock”. Also, the rail cannot move because it’s integral or also permanent bonded. And when that rifle is combined with certain scope makes and models- it never is off zero. For thousands of rounds the zero doesn’t change at all. But not everyone is using that rifle or those scopes. So experimentation is done- the rifles that don’t lose zero are paired with scopes that seem to lose zero or have issues, and the scopes that don’t have issues are paired with rifles that seem to have issues.

This takes a life of its own and you and your buddies start trying every combo just to see what happens. After tens of thousands of rounds, dozens and dozens of scopes, dozens of rifles, some clear evidence again points to some rifles and scopes don’t have issues, and most have constant issues. Through this a “best practices” for assembling rifles and mounting scopes comes out. A process that all but eliminates zero shifts. However, scopes are still being shot with, hunted with, and competed with that are failing. The long answer shorter is you find out that no company* is actually conducting “testing” for zero retention and tracking. One does, and that also happens to be the scopes that have by far the fewest failures in use- the only scopes that your group has to four to be trustworthy with almost no questions even in heinous abuse.

So once again you continue wanting to find a way to make sure a scope won’t lose zero in the field on a hunt for instance. You’ve eliminated the rifle as a cause. You’ve eliminated the mounting system as a clause. And you’ve found scopes that hold zero with utter greed, and that don’t ever cause issues. After the fiftieth tile that someone’s rifle gets knocked over and has to be rezeroed, you realize that drops and impacts cause loss of zero. So yiu zero your rifle and drop it. Then you keep doing it. Then some of your buddies join in. Some don’t, saying that you are stupid for purposely doing it, and that it’s just abuse. But after a while of getting “data” about what dropping does to the scopes and those buddies still missing animals or having to rezero, they start paying attention. Lots of scopes (and rifles) are broken in this process. You learn that only one or two can survive a shoulder height drop on concrete or being thrown down a range with breaking a turret or eyepiece off And those things are a bit silly for most uses (but not all). But it does become clear that dropping the scopes and checking for loss of zero is valuable, it’s just that a standard needs to be used for some level of consistency.

Eventually a standard is developed that has direct correlation to expected performance in the field- scopes that pass the “tests” never or very rarely have failures on hunts or in use. Scopes that do not pass it, consistently do. The rifles used are standardized for durability and weight plus or minus because heavier weight equals more failures. The mounting system is standardized because its never seen to be the cause of problems. The thing that the rifles are dropped in is standardized to be repeatable for multiple people, and multiple ranges. The height of the drops is experimented with until two heights and three events are found that cover most impacts-

1). Normal but not abusive- 18” single impacts

2). Hard impacts- 36” single impacts

3). Very hard use or impacts- multiple 36” impacts


And those roughly translate as-

1). Normal (18”) is about what one gets if a rifle is leaned against a truck or tree and gets knocked over, or a minor slip that causes one to catch themselves with the rifle in their hand.

2). Hard is about what one gets if the are climbing and slip on rocks or hard ground and the rifles is dropped or impacts directly; or if the rifle is stroked to the pack and the person falls with the rifle hitting the ground or an object.

3). Very hard use is the rifle coming undone from the pack and dropping scope first on the ground, or the person falling while climbing in a shake slide and the rifle rumbling a few feet down the hill.

It’s also noticed that scopes that don’t hold zero from 18” drops fail at an alarming rate from just normal, non abusive use. To the point that if it won’t hold zero from multiple 18” drops it’s known that it will lose zero or fail eventually, and usually quite quickly. It’s also noticed that if a scope model will consistently hold zero through the single 18” and 36” drops, but lose zero through the 3x3 36” drops, it will survive most general use without many issues, and can be a workable option, though eventually they have problems. And when a scope makes it through the whole eval, issues of any kind even with seriously horrible use are so rare as to be almost unknown.

In fact, only one scope out of hundreds has ever passed the whole thing and ever lost zero or failed in actual use.


Cont…

 

[Formidilosus]

How to take the results:

Taking the results is up to each person. Using a consistent as possible eval that people can replicate has massive validity. It’s very clear that scopes do not do what manufactures say they do, and that there are only a few makes/models that actually work like one would expect an aiming device to perform. It’s obvious in lots of use that if a scope doesn’t at least get a “PARTIAL PASS” from the standards above, it shouldn’t be used for anything that someone cares about at all.
Shooting pigs over a feeder- yeah ok, who cares. Going after meat does- aka food, maybe you should. An out of state or a buck hunt where missing will upset you, definitely. If it’s a once in a lifetime hunt or animal, or you’re the type of person that really truly doesn’t like failures, you want the scope that passes everything, and lasts for thousands of rounds in use consistently.


For me I wouldn’t use a scope that “FAILS” on a squirrel hunt, or waste a single dollar buying one- they are complete junk. I might would use a “PARTIAL FAIL” scope if I already had it and the use didn’t matter, or it fit a super specialized use that no other scope can meet that actually works. But for me, still no. I don’t like things that fail, I don’t like missing animals, and I really don’t like wounding them. A fail will miss or wound animals at sub 200 yards eventually. A partial fail will eventually miss or wound an animal at sub 400-500 yards. A PASS won’t cause a miss or wound from incorrect function unless it’s physically broken.

 

[Formidilosus]

Not every single scope will go through the full eval. Some scopes are known to adjust correctly and consistently, and any issues would be seen in live fire. Every scope will go through the zeroing, RTZ, live fire tracking, and drop evals however.

 

[Bones]

Thanks Form. Appreciate it!

 

[Woodrow F Call]

Am I going to have to sell my scope and buy something else?

 

[Bluumoon]

Great read, much appreciated! Lets say I've followed your recs on scope selection (SWFA 3-9s in Talleys and a 6x in Sportsmatch) and mounting procedure, would you advise that each setup be subjected to the "test"? Admittedly I cringe at the thought of dropping my Barretts, the Tikka wouldn't bother me in the least.

 

[Formidilosus]

Great read, much appreciated! Lets say I've followed your recs on scope selection (SWFA 3-9s in Talleys and a 6x in Sportsmatch) and mounting procedure, would you advise that each setup be subjected to the "test"? Admittedly I cringe at the thought of dropping my Barretts, the Tikka wouldn't bother me in the least.

No I would not say that. While I think everyone should see what their setup does, I don’t think everyone needs to put all of their gear through that. I would suggest if it is new or unknown items to check and test them thoroughly, how someone does that is up to them.

 

[ChrisAU]

Make me head of marketing for a solid scope company for a day.

A full page ad of a hunter dejected with his head down, empty pack, truck in the background as he heads to it…”Zero Retention Matters.”

Why this isn’t more important to more people is lost on me.

 

[ljalberta]

Great thread. I appreciate your insight you share on this site. It has spurred on a big transformation in my approach to scopes and shooting in general.

 

[Sandstrom]

Really looking forward to this, and thank you in advance!! Obviously there will be costs involved for this, is there any way we can donate???
Ryan

 

[Rob5589]

Make me head of marketing for a solid scope company for a day.

A full page ad of a hunter dejected with his head down, empty pack, truck in the background as he heads to it…”Zero Retention Matters.”

Why this isn’t more important to more people is lost on me.

The average guy wants the clearest glass, everything else is a distant 2nd, 3rd, 4th, etc.

 

[Trial153]

Make me head of marketing for a solid scope company for a day.

A full page ad of a hunter dejected with his head down, empty pack, truck in the background as he heads to it…”Zero Retention Matters.”

Why this isn’t more important to more people is lost on me.

Sounds like an Ad for the latest ED Meds..

 

[MTMeatHunter]

@Formidilosus, I’ve already learned a ton from lurking through your posts for years. Thank you for taking the time to post the data that you do. Is there someplace you might point me for an up to date and comprehensive list of scopes you’ve put through their paces, with their associated grades (PASS, PARTIAL FAIL, FAIL)? I apologize in advance if it’s readily available and I’ve just missed it. All the info is very much appreciated!

 

[Carl Ross]

But after a while of getting “data” about what dropping does to the scopes and those buddies still missing animals or having to rezero, they start paying attention. Lots of scopes (and rifles) are broken in this process. You learn that only one or two can survive a shoulder height drop on concrete or being thrown down a range with breaking a turret or eyepiece off And those things are a bit silly for most uses (but not all). But it does become clear that dropping the scopes and checking for loss of zero is valuable, it’s just that a standard needs to be used for some level of consistency.

Eventually a standard is developed that has direct correlation to expected performance in the field- scopes that pass the “tests” never or very rarely have failures on hunts or in use.

You know this has been a subject of interest to me for a while. For anyone who has started down this rabbit hole themselves, you'll probably identify with the line I bolded above. Once upon a time I was interested in working towards a standard for a drop test, but breaking scopes and rifles and warrantying them, along with the lesser wear and tear on expensive gear eventually tempered my enthusiasm before I got anywhere conclusive. The time, hassle, ammo cost, and other expenses can really add up. In that context, I'm excited to give this a try. First step will be to have a rifle system pass the proof testing... I think I'll use one of my lighter setups, as I'm not ready to drop a 20 lb full PRS rig on top of my personal scopes just yet.

The initial testing I did years ago did lead me to a place where the large zero shifts I used to see have pretty much been eliminated, but I have had my share of .1 to .2 mil shifts to chase. To anyone who doesn't think that's a big deal, I present the following:

Lets say your rifle shoots .5 MOA (as in, can hit a .5 MOA target every time, a very tall order). But occasionally, it will experience a shift in zero of up to .2 mil. Well, that .2 mil is a shift from center, so it can go in any direction. It needs added to the group size as a RADIUS, not a diameter. So... .4 mils is 1.4 MOA. Your .5 MOA rifle combined with a .2 mil potential zero shift leads to a 1.9 MOA system. Have had it happen, in a match, this past year. It definitely affected the match results. Had I been shooting animals instead of steel, it would have been a miss or a wounded animal.

*** To anyone whose going to try this for the first time, beware that a shooting mat over concrete will beat your gear up WAY worse than a shooting mat over dirt. If you want to try THAT, go in with proper expectations - you're going to be lowering the resale value.

 

[CoffeeGoat]

Make me head of marketing for a solid scope company for a day.

A full page ad of a hunter dejected with his head down, empty pack, truck in the background as he heads to it…”Zero Retention Matters.”

Why this isn’t more important to more people is lost on me.

I think you're probably right that it's important - but to @Formidilosus point, most people aren't competent enough shooters to know it was the gear's fault. I distinctly remember wounding a doe and being sure it was just me screwing up the shot. It took a bunch of learning and after the fact debugging to figure out the main cause. I think most scope manufacturers know that most shooters won't do that, why solve a problem "no one has."

 

[TNKnoxville]

You are evil. I'm an engineer and can't resist this type of testing...ahhhhhh. I hope the scopes I have don't fail!!!!!!

 

[Balderdash]

As Hunter S Thompson stated about the edge - The only people who know where it is are the those who've gone over it. So, too, it is with testing gear.

 

[Shraggs]

Yet another great gesture Form, really appreciated !