Benchrest Scopes

[Boyd Allen]

How would a scope manufacturer test POI shift? I understand how they might check tracking, but what specific equipment do they have to simulate conditions when scopes are installed and fired?

Back in the day, a friend and I set up a scope rack with several bases on a single plate that was part of an assembly that could be set on a table. Windage adjustable rings were used and a single scope used to align them to a target. All of the available 36X scopes were installed. The spacing was as close as practical. We set the device up at a registered match and invited shooters to look through the scopes, allowing them to make any adjustments that they wanted. This was the best method for comparing subjective evaluation of scope optics that I have heard about. Perhaps it is time for someone to do it again with today's scopes. The scopes were a B&L, two different models of Tasco, a Weaver, and a Leupold. The bases were one piece Weaver, designed for a 336 Marlin (flat topped receiver), and the rings were Millet. I probably should add that I agree that for benchrest, that having a scope not move is paramount. I find that shooters are often distracted from this by differences in image quality.

 

[Andy Cross]

Most can and do

How would a scope manufacturer test POI shift? I understand how they might check tracking, but what specific equipment do they have to simulate conditions when scopes are installed and fired?

Back in the day, a friend and I set up a scope rack with several bases on a single plate that was part of an assembly that could be set on a table. Windage adjustable rings were used and a single scope used to align them to a target. All of the available 36X scopes were installed. The spacing was as close as practical. We set the device up at a registered match and invited shooters to look through the scopes, allowing them to make any adjustments that they wanted. This was the best method for comparing subjective evaluation of scope optics that I have heard about. Perhaps it is time for someone to do it again with today's scopes. The scopes were a B&L, two different models of Tasco, a Weaver, and a Leupold. The bases were one piece Weaver, designed for a 336 Marlin (flat topped receiver), and the rings were Millet. I probably should add that I agree that for benchrest, that having a scope not move is paramount. I find that shooters are often distracted from this by differences in image quality.

When you are talking about an application specific optical device such as a scope which won't be used on anything else except a rifle then most manufacturers can and do test for POI shifts even if it has been returned for something else. The devices they use to shock the scopes vary depending on each companies test criteria. The shifts are measured with pretty sensitive instrumentation which has been calibrated to ISO standards. As your test at the range involved the human eye as an evaluation tool means I can't accept the findings as valid. You have to wire out human involvement as much as possible when doing this type of testing otherwise it becomes as much a test for the optical system in your head as anything else.

 

[Boyd Allen]

Sorry, but that last part just does not fly... for me. We put the scopes side by side so that a shooter could simply shift his head from one to the other, to make comparisons, and allowed them to make any adjustments that they wanted. PEOPLE use these scopes, not instruments. In discussions between experienced shooters who are familiar with scopes used in benchrest I have found that there seems to be a lot of agreement about which scopes have the best optics. The last time that I was tested, my corrected vision was 20-15 and my color vision is excellent. In short, I believe what my eyes tell me. I have also taken the time to learn what various optical faults look like, having spent some time in photography, starting back in the 50s. Having said that, any change in my scope inventory will be almost solely based on how solidly it holds its adjustment.

Without getting into too many details, some time back, a friend bought eight identical 45X scopes and used a Hood scope checker and a known quantity reference scope to check them for point of impact shift. Half of them showed movement ranging from .020 to .060 at 100 yards. The movements did not all show up immediately. I believe that he said that the direction of shift was the same for all of the scopes that moved. If scope manufacturers have effective ways of testing for this, given that these were top level scopes, how did it happen that there was a 50% rate of defect? If some of his scopes had to be fired a number of times before movement showed up, would factories run their tests enough times to recreate the problem? Admittedly this is a tough area, and there are ample opportunities for shooters to blame the wrong thing for a problem, but we always have the option of comparing results with different scopes, letting accumulated target data tell us if our guess was correct.

 

[Andy Cross]

That's huge

Sorry, but that last part just does not fly... for me. We put the scopes side by side so that a shooter could simply shift his head from one to the other, to make comparisons, and allowed them to make any adjustments that they wanted. PEOPLE use these scopes, not instruments. In discussions between experienced shooters who are familiar with scopes used in benchrest I have found that there seems to be a lot of agreement about which scopes have the best optics. The last time that I was tested, my corrected vision was 20-15 and my color vision is excellent. In short, I believe what my eyes tell me. I have also taken the time to learn what various optical faults look like, having spent some time in photography, starting back in the 50s. Having said that, any change in my scope inventory will be almost solely based on how solidly it holds its adjustment.

Without getting into too many details, some time back, a friend bought eight identical 45X scopes and used a Hood scope checker and a known quantity reference scope to check them for point of impact shift. Half of them showed movement ranging from .020 to .060 at 100 yards. The movements did not all show up immediately. I believe that he said that the direction of shift was the same for all of the scopes that moved. If scope manufacturers have effective ways of testing for this, given that these were top level scopes, how did it happen that there was a 50% rate of defect? If some of his scopes had to be fired a number of times before movement showed up, would factories run their tests enough times to recreate the problem? Admittedly this is a tough area, and there are ample opportunities for shooters to blame the wrong thing for a problem, but we always have the option of comparing results with different scopes, letting accumulated target data tell us if our guess was correct.

For 50% of the scopes tested to show between 20 to 60 thou shift I would question the testing device and or the interpretation of the data. That's huge.To be that much out would mean a product recall and if it was the norm they would be out of business because no one would buy them. When you run those sort of tests getting a few shooters to haphazardly look through the various scopes would require you get the same people to do that twice a day for a period of say a 4 day shoot. They can't know which scope they are looking through and you would have to mix up the order they are in each time. You would need a sample of around 50 shooters of mixed ages. Then if there was a crook scope you might see a trend but chances are you wouldn't.

You mention photography. I have made my living for the past 20 years as a commercial and industrial photographer full time and still do consultative work in optical engineering. I have also made quite a few speciality lenses for cameras used in the scientific fields. Testing optics irrespective of what sort of system it is needs to be done in such a way that human interpretation makes up a very small portion of the intervening variables. Otherwise you won't know if it is at fault or you're just having an off day. Personally I would prefer to look at fixing the shooter before I begin dismantling a scope.

 

[glp]

So, given a choice...

between a scope that is CRYSTAL clear to your eye but shows POI change and one that is not quite as clear (but adequate) that is rock solid POI wise, which would you prefer for actually shooting the benchrest game ( group or score)? Certainly, both would be nice! I am with Andy here. There are days when my eyes just don't focus quite as well as others...diet, mood, cold, allergies, blood sugar levels, amount of caffeine I've consumed...so the only way to test optics is to take the human variable out.

I have done amateur astronomy since my teens. I have a very nice astro-physics ED apochromatic refractor. Plunk that thing down here in Maine on a summer evening, when the daytime temp was 89 F and after dark its rapidly cooling down to 60, and most will think the view is terrible. Optics 1) need time to acclimate to ambient temperature and 2) the atmospheric "seeing" determined by how turbulent the air layers are have a huge impact on what I think about the scope if I don't know anything about the physical surroundings and the external things that affect optical performance.

I always try to keep my rifle scope out of the hot summer sun. Leave the thing in the hot sun, take it under the shade of the shooting roof and all bets are off that you will not see a change in POI.

 

[Chism G]

Benchrest Scope

I learned this in Freshman Chemistry class. A test without protocol is just an experiment. Even if a few people agree with your findings(Samplings),it still does not validate your results(Findings. Further testing,with established protocol, is required to confirm test Validity.

I am not an Optical Engineer. I read this somewhere….That Eyes are like finger prints. We humans all see the World through different lens. Factor in the neurological,psychological,and physical differences of how we see and you can understand why we don’t all see the same thing when looking through a Rifle scope.

If I can see 22-6mm bullet holes at 200- 300 yds through my 40X Scope,and the POA is consistent,that’s all I care about.

I have a friend who has two 50X March scopes. Both are well past the 5yr warranty. He doesn't complain about the clarity. he just keeps on winning.


Glenn

 

[Boyd Allen]

A couple of things....lenses that are used for photography have to be good enough so that when the image is magnified that it holds up to the desired level of quality. In the case of a small negative, or sensor the degree of magnification used to produce a large image for viewing that can be quite a bit. On the other hand, optics that are designed for viewing distant objects directly are generally not subject to this requirement. Also, for camera, binocular and telescopes there is nothing comparable to an erector tube or a reticle involved. The primary issue is image quality, which can be a secondary issue with rifle scopes used for benchrest. As far as the comments about procedure and the validity of results go, I find it interesting that people are so impressed with their own conjecture, absent any attempt to make better comparisons or do their own formal testing. The work with the eight scopes was done before March scopes were available, and the person that did the testing is familiar to all of you. He is a very experienced shooter, with a lot of resources available to him. This was not a casual effort, and he came up with a fix, and tested that. It was precisely because of these issues that there was demand for a scope that cost over twice as much as those previously available, and before that, the use of frozen scopes with external mounts. The multi-scope test that I did a lot of work on, did not address the issue of internal shift at all, but it was a useful example of how shooter evaluations of scope image quality might be better facilitated. Scopes either move, or they do not. If they move a small amount and that is not consistent, without some test method that is designed to discover it, it is very likely to go unnoticed. That is why Charlie Hood came up with his scope checker. I have spoken with more than one very experienced benchrest shooter who has experienced a slight but significant improvement in overall accuracy, after switching scopes.

 

[BlackwellADB]

Private Message

You know I would almost be willing to bet a C note that if you sent most of those suspect scopes back to the manufacturer for POI testing they would come back with a clean bill of health. This is common. Why ? because the scope was removed from the rifle and taken out of those rings. No torque or twisting being applied to the carrier i.e. the tube. If the asymmetrical forces weren't excessive then the memory - for want of a better word - of the metal would return the internals back to their original positions. Then when tested it would return to the correct POI each time. Pity we can't send the rifle in as well because then the guys in the lab could tell you what has been done incorrectly. How much does it take to disrupt a scope this way. Not much when you are looking at the tolerances we need.

Andy,

I sent you a private message. Did you get it ??

 

[Andy Cross]

Andy,

I sent you a private message. Did you get it ??

Not sure what is going on. My computer my service provider or the BR central server. Can't navigate to the personal messages.

Andy.

 

[Boyd Allen]

I can get to mine.

 

[Andy Cross]

Finally got my issue sorted

Andy,

I sent you a private message. Did you get it ??

Yep. Finally got my issue sorted.

Andy.

 

[R.G. Robinett]

You know I would almost be willing to bet a C note that if you sent most of those suspect scopes back to the manufacturer for POI testing they would come back with a clean bill of health. This is common. Why ? because the scope was removed from the rifle and taken out of those rings. No torque or twisting being applied to the carrier i.e. the tube. If the asymmetrical forces weren't excessive then the memory - for want of a better word - of the metal would return the internals back to their original positions. Then when tested it would return to the correct POI each time. Pity we can't send the rifle in as well because then the guys in the lab could tell you what has been done incorrectly. How much does it take to disrupt a scope this way. Not much when you are looking at the tolerances we need.

If we could repeat the specific "tests", you'd likely lose this bet - the scopes in question were all mounted in Kelbly Rings - lapped and/or, lapped and bedded, with around 13 In. Lb. of torque - the exchange involved simply sliding the scopes on/off the [full-length, one-piece) dove-tail bases. What would introduce different/additional stress?

Some scopes, "right out of the box", just will not hold POI. The Hood checker, or, a rail-gun, which will accommodate mounting multiple optics, will demonstrate this pronto. I'm not trying to bad-mouth scope manufactures - just stating real-world experiences - scopes aren't all perfect. Further, they do "wear out" - have lenses come loose, etc.

In the cases I've been exposed to, the individuals had all, "brand new" [6ppc] rigs, right down to the scopes - all day tuning sessions had resulted in ho-hummer, .300" plus agging capability . . . simply sliding off the offending scope, and replacing with a proven scope produced low ans sub .20" groups- when you're there, and observe the difference, it's difficult to deny that it's real. RG

 

[Andy Cross]

I didn't say

If we could repeat the specific "tests", you'd likely lose this bet - the scopes in question were all mounted in Kelbly Rings - lapped and/or, lapped and bedded, with around 13 In. Lb. of torque - the exchange involved simply sliding the scopes on/off the [full-length, one-piece) dove-tail bases. What would introduce different/additional stress?

Some scopes, "right out of the box", just will not hold POI. The hood checker, or, a rail-gun, which will accommodate mounting multiple optics, will demonstrate this pronto. I'm not trying to bad-mouth scope manufactures - just stating real-world experiences - scopes aren't all perfect. Further, they do "wear out" - have lenses come loose, etc.

In the cases I've been exposed to, the individuals had all, "brand new" [6ppc] rigs, right down to the scopes - all day tuning sessions had resulted in ho-hummer, .300" plus agging capability . . . simply sliding off the offending scope, and replacing with a proven scope produced low ans sub .20" groups- when you're there, and observe the difference, it's difficult to deny that it's real. RG

I didn't say at any time there were no bad scopes out there. Nor did I say they were ever perfect and I didn't say they didn't wear out. All I am saying is that the majority of bad scopes often aren't. It's the shooters eye sight, how well he or she can shoot on the day and those that do have poi shifts are often a lot smaller than the error that's printed on paper. To show up the real differences in a shooting situation I'd like to shoot a rail gun in a 100 yd vacuum chamber. Something like that might be doable in the USA but not here.
There are means of making optical systems that would not move at all called electromagnetic tracking optics. But to make such a syatem fit the size and weight restrictions suitable for a scope would mean paying 50K or more for a scope.

 

[R.G. Robinett]

And I didn't presume that you meant that!

I didn't say at any time there were no bad scopes out there. Nor did I say they were ever perfect and I didn't say they didn't wear out. All I am saying is that the majority of bad scopes often aren't. It's the shooters eye sight, how well he or she can shoot on the day and those that do have poi shifts are often a lot smaller than the error that's printed on paper. To show up the real differences in a shooting situation I'd like to shoot a rail gun in a 100 yd vacuum chamber. Something like that might be doable in the USA but not here.
There are means of making optical systems that would not move at all called electromagnetic tracking optics. But to make such a syatem fit the size and weight restrictions suitable for a scope would mean paying 50K or more for a scope.

Just that ho-hummer optics are not as uncommon as we'd like them to be. RG

 

[Boyd Allen]

Andy,
Are you familiar with Jackie's method for "freezing" a scope?
Boyd

 

[Al Nyhus]

Just that ho-hummer optics are not as uncommon as we'd like them to be. RG

Agreed, Randy. And I can't stress enough how important it is to have a baseline scope to go to as a standard. I have an old ironball test scope that looks like it's been drug down a gravel road behind a feral dog . But it absolutely, positively repeats shot after shot. Heck, I even put it on my hunting rifles when doing load work.

My 13.5 lb. Panda with a NF 12-42 was always used as a test platform for new barrels that were destined for my Kodiak actioned HBR gun. The one 'ho-hummer' I found using this method saved me three or four times the cost of a new barrel when considering components, travel time, motels, etc. etc.

Good shootin'. -Al

 

[Andy Cross]

Yep

Andy,
Are you familiar with Jackie's method for "freezing" a scope?
Boyd

Yep. Looks like it would probably work but don't think it would offer much immunity against thermal expansion and contraction shifts between the different materials used. Even though I expect it could be unfrozen would you want to do that to a new scope that hasn't yet proven to have a problem and trash your warrantee ?

 

[Boyd Allen]

The movement issues have pretty well been tracked down to the turrets and the pivot of the erector tube assembly as the main culprits, along with lenses coming loose after O rings harden and shrink. Based on performance, his system worked, and the rings that he used did not restrain the scope axially, so there was little chance for differences of material expansion rates to create stress.

The fellow that I mentioned doing the testing on the Leupolds was responsible for the creation of the March brand, in that he came up with the money for the rather substantial minimum order requirement for the first 40X scopes before handing off the distribution to Kelbly's. He had tested a prototype that Turk Takano had brought from Japan. Before that, Dion had been a design and prototype business. It was my friend's determination that the prototype did not move, that moved him to pay for the initial order, because that was the only way that they would produce the scopes that he wanted.

The whole issue of POI movement has been a hot and continuing topic in short range benchrest for quite a while. As a result better products are being made. The methods for finding movement may not fit your expectations but they have been effective, and more importantly, someone actually did the work.

 

[glp]

i recall him

Yep. Looks like it would probably work but don't think it would offer much immunity against thermal expansion and contraction shifts between the different materials used. Even though I expect it could be unfrozen would you want to do that to a new scope that hasn't yet proven to have a problem and trash your warrantee ?

saying years ago when he did freezes, that he epoxied the erector tube in with bushings, which would make it virtually impossible to remove or so it would seem. Bracken does do a reversible freeze, no idea to his method. Thermal expansion is always a problem. I do my best to keep my scope in the shade and keep a sharp eye on POI as the day warms up.

 

[ebb]

scopes ?????

Andy If scope makers are making a scope that wont work with a substantial number of users eyes and can be warped in rings or bases that come on production and custom rifles . Who are they making scopes for? They need to work in the real world, with real people. If all of these reasons you are giving are the real reason for scope failures, or how ever you want to say it, then they are building a product that doesn't meet the needs of the customers. You would think at least one manufacturer would know this and redesign the scope to work around these issues and produce a scope that held POI. You also said that on 3 companies make optical glass and the glass isn't the reason some are clearer than others. Does this mean that all of these companies make glass that is of exactly the same quality? I don't understand why a scope you pay so much money has to have so many excuses made for it.