Posts Tagged ‘Optics’
by Tom Gaylord, a.k.a. B.B. Pelletier
Today’s lesson is about sighting-in a rifle scope. I know that scope mounting and sighting-in seems daunting, but it isn’t as hard as you might imagine. In the last report, I sighted-in at 10 feet. Because I got lucky, it took just 2 shots to sight-in the rifle; and when I finished, I told you I was ready to try the rifle at 25 yards. I said, based on the results of my 10-foot sight-in, it should be on paper at that distance (actually it would be on target at any distance between 20-35 yards, given the TX 200′s velocity), but it probably wouldn’t be exactly where I wanted it. Today, we’ll find out if that prediction is correct.
Let’s get to it
So, I set up the bench and started shooting at 25 yards. I chose H&N Baracuda Match pellets because they were the pellets I used at 10 feet. If you forget what happened during the 10-foot sight-in, you really should read that report first to appreciate what’s happened here. A quick summary would be that I guesstimated how high above the bore the center of the scope is, and shot at a dot the same distance above the desired point of impact. Aiming at the upper dot, I was trying to get the pellet as close as possible to the dot beneath, which meant the scope would be shooting to exactly the point of aim (offset by the scope and barrel centers) when all trajectory was removed from the equation.
The two dots are separated by approximately the same distance as the center of the barrel and the center of the scope. Aim at the top dot and hit the bottom dot. This is the first shot. After I adjusted the scope, the second shot went through the bottom dot.
Shooting at 25 yards
The first shot at 25 yards landed slightly above and to the left of the bullseye. I then shot 4 more that moved over to the right just a little. I took the center of the larger 4-shot group as the place where the scope was really sighted, and I adjusted from there. In all it took me far less than 10 minutes to sight-in this scope, even though I spread the reports over a period of 2 weeks.
The first 5 shots at 25 yards landed high and to the left, with the very first shot landing farthest to the left. I took the center of the main group of 4 to be the point of impact. From there, I adjusted the scope down and to the right.
Bear in mind that I do not want to hit the dot at the exact center of the bullseye, if possible. That’s my aim point; and if I destroy it, I have to guess where to hold the crosshairs.
Now that the rifle is sighted-in, I shot the first 10-shot group at 25 yards with the stock rested on my open palm, next to the triggerguard. I got a fairly good 9-shot group, but I managed to throw one shot to the left. Nine went into 0.376 inches, but that one stray shot opened the group to 0.605 inches. I was moving around too much in the artillery hold, and I could see it through the scope.
Stability seemed to be my problem, so I slid my off hand out to where I could feel the cocking slot on my palm. The rifle seemed to rest steadier, but the group doesn’t reflect that. Ten pellets went into 0.714 inches, which is horrible for a TX200. Obviously, this wasn’t the right hold for the rifle. And just as obviously — I was having a bad day.
Sometimes, a disaster (okay, maybe just a small setback) contains the seeds of discovery! Since I couldn’t hold the rifle steady enough to shoot a good group on this day, could I rest it directly on the sandbag and do better? We’ve been interested in the fact that some spring guns don’t seem to need the artillery hold. I already told you the TX200 is one of them. Perhaps, this was the day to find out.
For the next group, I rested the rifle in the long vee-groove in the top of my sandbag. The bag is so long that the rifle rests there without needing a rear bag for support. It was dead-steady when I sighted this time.
The results tell the story! This time, all the shots went to the same place. The group is very round and tight, at 0.336 inches. This is clear proof that the TX200 can be bag-rested when shot, and also that the rifle is incredibly accurate. I’ve shot even better groups with it in the past; but whenever I do things right, I always get good groups with this rifle.
Notice that in today’s test only a single type of pellet was used. That kept things simple and allowed me to look at other things without worrying about which pellet to choose.
So, we’ve learned 2 things. The first is that it’s easy to mount a scope on an air rifle and to sight it in. It doesn’t take a lot of time, nor do you need any fancy equipment. Of course, if your rifle has a drooping barrel problem there will be more to do, but these are the basics.
Second, we’ve learned that the TX200 can shoot as well or better when rested directly on a sandbag as it can with an artillery hold. That’s certainly true if you’re shaking when holding the gun.
Tomorrow is the 50-yard test, followed by a full test of a brand-new TX200 Mark III, I hope. There are some other things that can be explored with this rifle as our testbed. All in all, we have a lot of things left to do with this air rifle!
by Tom Gaylord, a.k.a. B.B. Pelletier
Parallax is an optical term describing how the point of view affects what the viewer sees. The driver of a car may see his speedometer needle at 60 m.p.h, while a passenger to his right may see it hovering just above 57 m.p.h. In the UK, the passenger is on the driver’s left and the speedo needle will appear to be over the 63 mp.h. mark. The needle hasn’t moved in either case, but the observer’s viewpoint has moved.
And so it is with a scope. You look through it and see the crosshairs exactly in the center of the bullseye; but if you move your head on the stock, the crosshairs will also appear to move slightly. So, where you hold your head relative to the scope determines where the scope appears to be “looking.”
Many scopes today have a parallax adjustment. Some scope manufacturers call this an adjustable objective, or simply AO; but that just stems from the fact that it is the objective bell that’s turned to correct for parallax. On other scopes, this adjustment is a knob on the left side of the adjustment turret.
The adjustable objective is an objective bell that turns to remove as much parallax as possible. The scale on the bell indicates the yards to the target that have been focused.
On scopes with a sidewheel parallax adjustment, a knob on the left side of the turret adjusts for parallax. This is much easier to reach than the objective bell when holding a rifle.
The parallax adjustment adjusts the scope lenses so the least amount of parallax exists at that distance (the distance to the target). To the shooter, it looks like the scope is focusing on the target. But here’s the important point: No amount of parallax correction is ever enough. There will always be some parallax in the scope, no matter how well it’s been adjusted. Where you hold your head on the stock is very important, whether or not your scope has a parallax adjustment.
Range of scope adjustability
Every modern scope comes with vertical and horizontal adjustments, so the crosshairs may be adjusted to the point of pellet impact. Open sights often have these same adjustments. But there’s one big difference between an open sight’s adjustments and those of a scope. As an open sight is adjusted, the sight is moved mechanically. Usually just the rear sight moves, but sometimes the front sight moves, as well.
When a modern scope is adjusted, you cannot detect any movement. It’s inside the scope but can’t be seen from the outside.
What gets moved isn’t the scope tube, but a smaller tube inside the outer tube. This inner tube is called the erector tube, and it contains the reticle and other things. The wires or lines of most reticles do not move when adjustments are made. Instead, the entire erector tube moves, carrying the reticle lines with it. Since the lines are fixed, they always appear to be centered when you look through the scope.
There are some scopes that do have moving reticle lines. These are older technology scopes and are often from Germany or Russia. But these are so infrequently encountered on the modern market that they aren’t worth discussing.
I’ve mentioned the term modern in relation to the scope of today. Fifty years ago, there were scopes that did not contain erector tubes. Instead, these scopes were adjusted from the outside, so their entire tubes moved whenever adjustment were made. The adjustments were in the scope rings.
This vintage Unertl scope is held in spring-loaded rings that adjust the whole scope like the erector tube in a modern scope. The spring is inside the button at the 4 o’clock position and works for both the vertical and horizontal adjustments.
The section of the modern scope that contains the adjustment knobs is called the turret.
By looking at vintage adjustable scope rings, we can see how the erector tubes inside modern scopes move when they’re adjusted. And this is what is important. The adjustments work against a coiled steel return spring that pushes the scope back when the adjustment screws are backed off.
When the scope is adjusted higher or to the right, the erector tube springs expand and lose their tension. At some point, which differs from scope to scope, these springs relax. That’s when the scope no longer holds a zero and won’t adjust in that direction anymore.
This scope’s elevation knob is adjusted as high as it will go. The erector tube spring is fully relaxed, and the scope will be free to shift. It would be better not to adjust this scope above the horizontal No. 3 line.
Quality scopes have more adjustment range than cheaper scopes, but all scopes have difficulty adjusting out to their upper and right limits. As a general rule, I tell shooters they should never adjust beyond the three-quarter point in the high or right directions.
People sometimes ask if there’s a problem when adjusting the other way (down or to the left), and I tell them there isn’t. All you do when you adjust all the way down or to the left is compress a coil spring until it’s coil-bound. That doesn’t damage the scope, nor does it affect accuracy in any way.
Scope sights are wonderful tools that can enhance your shooting experience. They’re not magic, however. They operate by rules, just like anything else. Learn how they work, and they’ll do their part to make your shooting more successful.
by Tom Gaylord, a.k.a. B.B. Pelletier
This article was originally written for the upcoming Pyramyd Air catalog. But there were so many new rifles and pistols that we didn’t have room for this. I felt it was important enough to get it out, so I’m publishing it on the blog.
You’d like to have a scope; but when you check into the subject, it gets very confusing, very fast. In this 2-part blog, we’ll explore the basics of scopes.
A telescopic sight, or scope, is a type of sight that magnifies the target, usually making aiming easier. It may have a fixed amount of magnification or the magnification may vary within a range, allowing the shooter to select what he wants.
Inside the scope are lines called reticles. One runs up and down and the other runs side to side. They intersect in the center of the field of view. They are the aim point that’s put on the spot where you want the pellet to go. They adjust in both directions, but you never see them move. They are held inside a tube inside the scope; and when they’re adjusted, the entire tube moves so they always appear centered.
If your rifle is sighted-in, the pellet should land fairly close to where the intersection of the reticles was when it fired. How close it lands depends on several things—how accurate the rifle is, how well it was held when it fired, how good a pellet you use, the weather conditions (especially the wind) and so on.
The rifle is always moving!
The first thing that surprises someone who looks through a scope for the first time is that the rifle is always moving. In the movies, the camera sometimes looks through scopes that never move; but in real life, they’re never still. The rifle is also moving when you sight with open sights; but since the target isn’t magnified, you cannot see the movement.
Just because there’s a scope on your rifle doesn’t mean it will be more accurate. You have to find ways to slow the movement and to eliminate or minimize it as much as possible. Once you learn to do this and to follow through after every shot, you’ll be rewarded with better groups and more accurate shots.
More magnification may not help
You would think that because a scope magnifies the target it automatically makes it easier to see and hit. Sometimes it does, but other times it does the opposite. When the magnification is too great and the target area is dark, you may not be able to find the target in the scope. When you hunt in the deep woods, for instance, a 4x scope will do a lot better than a 16x scope. You may be able to see the veins on each leaf through the 16x scope, but which leaf are you looking at?
Greater magnification also can make the image seen through the scope darker, and it may even appear as though it’s in fog. On every scope that has adjustable power, the amount of light that gets through the scope decreases as the power increases. This effect is offset by superior quality lenses and by special lens coatings, but the budget brand scopes don’t have these things.
Magnification — use what you need
Why do airgunners need so much magnification? Well, most of them don’t need it, but one group does. The field target shooter uses his scope to help determine the range to the target, so he can know where his pellet will be in its trajectory when it arrives on target. The difference of a yard or two can make the difference between a hit or a miss.
A field target shooter wants to see the smallest object he can possibly see at the farthest distance on the course, which is 55 yards. He’d like to be able to see a blade of grass so clearly at 55 yards that when he adjusts the parallax he can see the image come into sharp focus. If that blade of grass is standing next to the target he wants to shoot, he’s just determined the range to the target.
It takes a lot of power to see a blade of grass clearly at 55 yards in a dark forest setting. So, field target shooters use scopes of 32x, 40x and even 60x to resolve things this small. These scopes aren’t too useful for most shooting; but for the rangefinding task, they excel.
Most airgunners will do very well with 9x, 12x and even 16x. Scopes of that power will be smaller and lighter, and that translates to less fatigue while hunting. A squirrel hunter in the deep woods can get by with even less power. Maybe 6x is all he needs. Benchrest target shooters, on the other hand, have a stable platform and can spend some time finding the target in the limited field of view that a powerful scope gives. For them. the most important thing is being able to bisect the target as precisely as possible, so every shot is aimed at the same place. Understanding what magnification you need and matching it to your sport is one of the things that increases satisfaction when shooting airguns.
Understanding scope adjustments
Most shooters know there are both vertical and horizontal adjustments available on a scope. They’re called elevation and windage adjustments. Here are some facts about adjustments that you may not know.
First of all, no scope adjusts exactly by a quarter minute of angle or an eighth minute of angle. When they say these things, scope manufacturers are only making approximations. The scope adjustments depend on the thread count of the adjustment screws, and the manufacturer will round this up or down to give an approximate distance the crosshairs move. This is given in minutes of angle, and the most common understanding is at a 100-yard distance, where a minute of angle is very close to one inch. So, a scope with ¼ MOA adjustment clicks is supposed to move the point of aim by a quarter-inch at 100 yards. It sounds great until you understand that everything is an approximation. The real distance that the crosshairs move with one click of adjustment may be 0.311 inches, but no scope manufacturer is going to put that on the box. So, they write that the scope has quarter-minute clicks, and you work it out when you sight in — unless you’re anal, which is where some shooters get into trouble.
These shooters arrive at the range with their scoped rifle and a notebook to record all the scope adjustments. Man — that is a heartbreak in progress! What will happen, if they stick to it long enough, is that they’ll discover that their scope actually adjusts by 7/19 of an inch per click. Most of them see the futility of trying to do it by the book and default back to adjusting the scope until their rounds strike the paper where they want them to…or as close as their scope can come.
Now, let’s talk about stiction, which is the scope’s unwillingness to move after being adjusted until it is hit with a large amount of vibration. Said plainly, the scope tends to stay where it was before the adjustment until the gun is fired several times and it finally “settles in” to the new adjustment. Put an eager-beaver shooter on that scope and have him try to sight it in, and you have the recipe for disaster. He’ll keep adjusting the knobs, all the while the scope is lagging behind each adjustment by two or three shots. The result will be a scope that wildly changes its point of impact as the frustrated shooter fails to comprehend that he’s causing the problem.
When a scope is adjusted, sometimes it takes several shots for the adjustments to be fully realized. This is called “stiction,” which is the resistance of the scope’s parts to movement after they’re adjusted. In this case, the first shot was to the left and low, where the scope had been before adjustment. Shot 2 moved to the right and up, and shots 3 through 5 are in a tight cluster in the new point of impact.
Not all scopes suffer from stiction. Of those that do, all won’t suffer by the same amount. Each scope must be taken as a unique entity, and the shooter has to have patience when adjusting it. This is the one time where three-shot groups are valid because they give the scope time to move to the new setting. But if the shooter doesn’t realize what’s happening, it can look like the scope is no longer able to hold a group because a three-shot group from a scope with a lot of stiction will look like a wild pattern. All you have to do is to continue shooting the gun, and things will settle down, again. But some shooters don’t have the patience for this.
Look for part 2 tomorrow.
by Tom Gaylord, a.k.a. B.B. Pelletier
As you read this, I’m driving to the Roanoke airgun show. This is just a reminder that I’d like you veteran readers to help answer the questions we get from the new readers while I’m away from my desk. I’ll read the comments a couple times each day and answer those I need to, but I don’t have as much time when I’m on the road. Thanks!
Today, I’ll mount a scope on the TX200 Mark III and sight it in. This is normally accuracy day, but I’m slowing down this report so I can explain several things that are usually glossed over — such as mounting a scope and sighting-in.
This report will look like a photo gallery. And the photos were all taken with flash because there are so many of them. I apologize for that, but I have examined each picture and you will be able to see each thing I refer to.
Let’s get started. Someone said I should used the Hawke 4.5 to 14 X42 Tactical Sidewinder scope, so that is what I mounted. I used a set of Leapers 30mm medium-height rings because they’re high enough for this scope and have the vertical scope stop pin that the TX200 needs.
Does the scope fit the rifle?
The first step in the process is to lay the scope next to the gun, positioning the eyepiece where you think it needs to be to fit your eye position. That will tell you how the scope is going to fit on the rifle.
Laying the scope above the rifle where the eyepiece needs to be tells us how the scope will fit on the rifle. Notice that the objective bell will hang over the loading port a little; but as I mentioned in Part 2, that’s not a problem.
Seeing that the scope will fit, the next task is to position the scope rings on the rifle. I used 2-piece rings, so I will first position the rear ring with the scope stop pin. The TX200 Mark III has three holes for a vertical stop pin. Pick the hole you like and make sure the stop pin fits into the hole when the ring is installed.
Adjust the vertical scope stop pin in the base of the rear scope rings so it goes deep into the hole on the rifle. On some rings, it will be necessary to peel up the anti-slip tape to access this pin for adjustment.
Now, you can mount the rear scope ring, making sure that the stop pin goes into the hole you’ve selected. Try to slide the ring to the rear of the gun so the stop pin makes contact with the rear wall of the stop hole. Then, you can tighten this ring in place.
Once the rear ring is positioned, you can position the front ring, using the scope as your guide. Leave room on both sides of both rings to slide the scope back and forth, if possible. This is where the advantage of 2-piece rings shows up.
Once both ring bases have been installed, carefully lay the scope in them and see how it fits the rifle.
Now that I know the scope fits as planned, I check it for fit with my eye by holding the rifle in a shooting position. The scope is still just laying in the bottom rings — the caps haven’t been attached yet.
By looking through the scope, I determine that the rings have been positioned correctly. I adjust the scope slightly to align the vertical reticle and also to position the eyepiece for maximum light when the rifle is held comfortably. The caps can now be installed and secured.
Aligning the scope
You can go through all kinds of machinations to align the scope perfectly vertical, but it doesn’t matter. What matters is that it looks vertical to you when you hold the rifle comfortably because that’s the way you’re going to align the scope every time you use it.
I used to do all sorts of things to “level” the scope before I finally understood that the scope will NEVER be level! Level is what looks level to you; and if you hold it the same way every time, that’s all that matters.
Now that the scope is mounted, it’s time to sight it in. For that, I made a white card with two black dots made by a felt-tipped pen. The top dot is my aim point and the bottom dot is as far below the top dot as the center of the bore of this rifle is below the center of the scope. That was just a rough estimate — I didn’t use a ruler. I’m going to sight-in the rifle at 10 FEET. That’s right — 10 FEET!
If this seems strange, you haven’t read my article about a 10-minute sight-in. When I worked at AirForce Airguns, I used to mount scopes and sight-in all the rifles that were sold directly by the company. It took less than 30 minutes from the time I was told what rifle and what scope was needed until I had the scope locked down and sighted-in at 23 yards. This procedure is how I did it so fast.
I step back about 10 feet from the card with the 2 dots and put the crosshairs on the top dot. I fired one shot. I used H&N Baracuda Match pellets because I know they do well in this rifle.
The first shot lands slightly high and to the right of the lower dot. Remember, the lower dot is where the pellet should go if it comes straight out of the barrel while the scope is aimed at the top dot.
Shot 1 was a surprise. Usually the first few shots are a lot farther off the mark than this. But I adjusted the scope from this — left and down.
How much left and down is not a precise thing. I do it by spinning both adjustment knobs and not even counting the clicks because I know that at 10 feet I have to move the crosshairs a lot to make them move at all. If I had to guess, I would say it was 16-20 clicks on each knob. Then, I fired the second shot.
Now, the rifle should be on paper and close to on-target at 25 yards. It may not be exact because this is a loose method — but it will be close enough.
Next time, I’ll shoot 25-yard groups, and I’ll start with where this sight-in lands me.
by Tom Gaylord, a.k.a. B.B. Pelletier
Today’s report is for blog reader J-F, who asked this exact question: “Why do airgunners need high-magnification scopes?” And let’s define high magnification as anything over 12x. That’s arbitrary, of course. It’ll be arbitrary no matter where you set the limit. I set it there because that’s 3 times the power that the average deer hunter’s scope had in the 1950s.
But airgunners delight in 24x, 32x, 40x and even 60x scopes. I know because I’m one who does. But I also know why I want this level of magnification and what purpose it will serve.
One reason for high-magnification scopes is pure bragging rights. Like the pilot who has to have the largest, most complicated watch, the biggest scope gets the most attention — at least in the minds of the guys who think that way. And I know for a fact that some people do think that way; I’ll tell you how I know in a moment.
One good reason for owning a scope with high magnification is so you can use it to determine the ranges to targets. No one needs to do that more than the field target competitor. Rangefinders are not permitted in field target matches, but the parallax adjustment on a scope provides something very close because it focuses the scope when the distance to the target is dialed in. This isn’t a true rangefinding function like you might find on a coincidence rangefinder built especially to do this, but it’s close enough to satisfy most people. And, it’s all you’re allowed to do.
Field target courses run from 10 yards to 55 yards, so the scope has to work in those boundaries. You want a scope that has most of its adjustment range between 10 and 50 yards. The best field target scopes are made that way — with 3/4 of the adjustment (the distance that the adjustment wheel or bell is turned) between those 2 distances.
To determine ranges accurately, you have to be able to see when something very small comes into sharp focus at your desired distance. To see things that small, you need as much magnification as you can get with the image still being clear.
The kill zone of this field target is the small hole above the dime. Your pellet has to go through the hole without touching the sides to score a point. This is why field target competitors need to know how far away the targets are!
Let’s get something clear right now. Just because a scope adjusts to 40x does not mean that you can use it at that setting. I own a Tasco Custom Shop 8-40X56 scope that cost $650 back in the 1990s, and it’s unusable above 30x for anything other than a bright target in direct sunlight. Field targets are often shot in the deep woods, where the light is either low or dappled with bright sun and dark shadows. In that light, my Tasco isn’t useable above 30x.
There are cars whose speedometers go up to 120 m.p.h. It doesn’t mean the cars go that fast. Same is true of scope magnifications levels. If you want to see at 40x in a field target setting, you’re probably going to have to pay close to a thousand dollars for your scope.
Small field of view
Here’s how I know that some people buy big scopes just to be envied. On several occasions, I’ve seen a field target competitor start the match and then not be able to find the targets! They sit there burning everyone’s time, looking though their powerful scopes but are unable to see the targets because everything looks so big and dark through the lens. This got so bad, in fact, that AAFTA (the American Airgun Field Target Association) started enforcing the time rules that typically give a competitor 5 minutes per 2-target (4-shot) lane.
The reason this happened is because these guys had never looked through their scopes at anything besides paper sight-in targets until the day of the match. They assumed things would be as they always were; and, of course, they aren’t when you move from a well-lit range into the woods.
The other thing powerful scopes do is bring out the anal side of some shooters. They will sit and range and rerange to the target, acting like some clueless manager examining a spreadsheet. They can’t get off the dime and take the shot because — what if they were wrong?
On the other hand I suffer from the opposite affliction. I don’t take my time and just charge on through the course. Great instincts for a first-wave armor officer — not so good for longevity on the battlefield or to win a match.
The other shooter who really needs a powerful scope is the benchrest shooter. “Aim small, miss small” is their motto. A few weeks back, I showed you my 100-yard box targets that help me sight my most accurate scoped rifles.
My best centerfire rifles are, in descending order — my Rock River AR-15, which I built from parts; my HW 52 in .22 Hornet; and my Savage 1920 bolt-action in .250-3000 Savage. The AR has the Tasco 8-40X56 scope on it; and even on sunny days, the power never goes above 30 or the scope gets foggy. The Weihrauch Hornet has a vintage Weaver K10-T that’s a fixed 10-power scope with an adjustable objective. The Savage is carrying a vintage Weaver V9-W 3-9X32 variable with a widefield view.
My 3 most accurate centerfire rifles are (from the top), AR-15, .22 Hornet falling block and .250-3000 bolt action.
One of the main reasons two of these scopes are vintage is that they have fine reticles that are perfect for my box targets. I can see when they split the box, even at these relatively low magnifications. Would I like more power? You bet! But I need to get it in scopes that will fit in fairly exotic rings and clear the guns when they’re mounted. That’s a tall order because high magnification usually comes with a large objective bell.
Who doesn’t need high magnification ?
As a general rule, hunters don’t need high magnification; and they do need the wider fields of view and brightness that come with lower-powered scopes. Varmint hunters might disagree with me on this because they’re more like benchrest shooters, but squirrel and rabbit hunters will probably agree.
Exterminators can also get by with lower power, with a few exceptions. When they hunt quarry that’s extremely wary, such as rats can sometimes be, they may want more power to place their pellets precisely on the little part of the animal that does show. But we’re talking 12-16x here — not 40! But the guy who’s killing birds in a discount store or mall at 3 a.m. can get by with a good 6x scope most of the time.
So, J-F, the answer to your question is a combination of things. There are those airgunners who actually do need high magnification, then there are the wannabes who have it because it’s cool. And then there are the first-time buyers who may get it because they have no idea what they’re getting into, and high magnification sounds good.
by Tom Gaylord, a.k.a. B.B. Pelletier
This is an ongoing series about scope questions and issues. Blog reader David Enoch asked for it originally, but many other readers have jumped in since it began. Today, I’ll talk about adjustable scope mounts.
First things first
Why do we need adjustable scope mounts? Aren’t the scopes, themselves, supposed to adjust? Yes, they are, but 2 things quickly become a problem. First, the scopes don’t adjust as far as we need them to; and second, when a scope adjusts toward its upper and right limits, it loses its precision. I will address the second problem because it’s really the principal one.
When we look at a scope, we see that it has a range of adjustability and assume that it’ll work as it should throughout this range. But that’s not the case. Inside each modern scope there is a smaller tube called the erector tube. The erector tube often contains the reticle; and as the tube moves up, down, left and right, so does the reticle. So, moving the erector tube is what moves the reticle.
There is a spring or springs that press against the erector tube, making it press against the adjustment knobs, in turn. That spring has a range of movement it goes through as the tube moves. When the tube is up high or far to the right, then a spring or springs that press it against the adjustment knob or knobs are relaxed and can allow the erector tube to move when the gun vibrates, such as with a shot. This is one of the chief causes for “scope shift.” You fire the gun, and the erector tube moves slightly, taking the reticle along with it, of course. On the next shot, the scope will be aiming at a slightly different place. It’ll appear that your scope is wildly throwing the shots around.
This elevation knob is adjusted up to its maximum limit. I recommend not adjusting it higher than the number 3 line on a scope like this to avoid scope shift.
I tell folks that a good rule of thumb is to not adjust their scopes above the 3/4 mark on the elevation knob or past the 3/4 mark on the right windage adjustment. Some scopes can adjust farther than this without a problem; but the closer you stay toward the middle of the range, the better. If your scope doesn’t have knobs like these, you may have to count the actual clicks of adjustment to know where you are.
Is adjusting the scope in the opposite direction (i.e., down or to the left) a problem? No, it isn’t. You can adjust all the way until the adjustments run out in the down and left directions. It doesn’t hurt the scope, nor does it affect accuracy.
So, the scope that you thought had a huge adjustment range turns out not to have as much as you believed. Yet, your airgun (or firearm) needs more adjustment than you have. How do you compensate for the adjustment you no longer have but may need? With a scope mount that adjusts, of course.
Adjustable scope mounts
The purpose of an adjustable scope mount is to align the axis of the scope in a direction different than the scope base on the gun dictates. If all scope bases were aligned with the axis of the barrel, there wouldn’t be a problem, but they aren’t. Adjustable scope mounts can compensate for this, leaving the scope’s internal adjustments to serve the ballistic requirements of the gun in question.
Up and down, left and right
A barrel can point off from a gun’s scope base in any direction, but the most common direction is down. The barrel “looks” down, in relation to where the scope tries to look. The other 3 directions are also possible, with left being the second most common. After that, the other 2 directions happen pretty infrequently.
So, if you’re going to need extra adjustments, it will most likely be extra “up” that you need, followed by extra “right.” Adjustable scope mounts have to provide extra scope movement in all directions, with up and right being needed most often.
Scope tube integrity
The scope tube is a hollow, rigid tube that must maintain its integrity to keep the lenses in alignment. If the tube were to bend, it could seriously damage or even break the scope. Adjustable scope mounts must either move the scope as a whole without putting any stress on the tube, something that only a 1-piece mount can do; or they must adjust in such a way that when the rear mount moves, the front mount can relieve the stress on the scope tube. Only the B-Square AA adjustable scope mounts were able to do that; and when B-Square sold the company several years ago, the new owner moved the manufacture of the AA adjustable mount to China, where the quality control was soon lost. You cannot buy new AA adjustable scope mounts any more.
When the rear mount is raised above the front mount, if the front mount doesn’t move to compensate, the scope tube will be strained. These B-Square 2-piece AA adjustable mounts have rings that pivot forward to allow the scope tube to remain straight.
Sports Match has 2-piece adjustable mounts on the market; but as far as I can see, they make no provisions for relieving the stress on the scope tube when the rings are adjusted separately for elevation. I guess I need to test them to learn their operational parameters. I don’t see how they can avoid stressing the scope tube when the front and rear mount are at different heights, but I’m willing to hold my opinion until I’ve examined them.
I’ve tested several 1-piece adjustable scope mounts and found all of them to work well in this regard. Most recently, I tested the BKL adjustable mount and found that it moved well in both directions.
What about precision?
To date, no one has made an adjustable scope mount that adjusts with precision for a modern scope. Such mounts do exist for vintage scopes that have no erector tubes because the entire scope has to be moved by the mount. I have shown you this kind of adjustable scope mount a couple times.
This Unertl scope ring adjusts to move the entire scope. It has the same precision as the adjustments on a modern scope.
Slippage is common with adjustable scope mounts
The most common problem is the adjustable scope mount that does not hold its position. That’s why the Chinese-made B-Square adjustable mounts failed. Their screw holes had sloppy threads that tore out under stress, and the mounts couldn’t hold in position. So, whatever adjustable mount you get, it must hold its position once it’s been adjusted, or it won’t work.
And slippage happens soonest on spring guns because of their recoil and vibration. Ironically, spring guns are the very ones that need the adjustable mounts most often. There’s nothing that can be done about this, but you must understand that you don’t want a scope mount that can’t hold its position.
Firearms shooters need adjustable scope mounts more today than ever before. I think that’s because modern guns are being assembled faster and with less precision than they were in the past. The thing is that firearms shooters are not as aware of scope problems as airgunners, so they tend to have more of them; and when they do, the problems are harder for them to resolve. I’ve tried to help people who I knew were having some common problems such as adjusting too high in the scope’s range, but they just looked at me like I was crazy. Surely, no scope manufacturer would field a scope whose adjustments were not 100 percent useable?
That’s all I have for you today. How about telling me your other unresolved scope issues?
by Tom Gaylord, a.k.a. B.B. Pelletier
Today, I’ll tell you how the latest 3-9X32 UTG Bug Buster scope works in action. As you know, this scope was mounted on the Evanix Rainstorm 3D bullpup rifle that I tested for you yesterday. While shooting it, I had the opportunity to examine the performance of this latest Bug Buster scope in great detail, so now I can report on that, as well.
A world of improvement
The last Bug Buster scope I used before this one was a fixed 6x scope that’s now many years old. This new Bug Buster is very advanced from that one, though there are some things that haven’t changed.
The first and most obvious improvement is variable power. Of course, Bug Busters have had variable power for many years, but I think this was my first chance to really use one. In the old days, we were just thrilled to have a fixed 4x. It was the ability to focus down to just 9 feet that was the big sales feature of the Bug Buster, and we didn’t expect much more than that. But variable power is usually better, since it gives you the opportunity to choose where to set the magnification. That being said, I cranked this scope to 9x and left it there. I doubt there are many reasons for me to ever use the lower power settings.
Field of view
The Bug Buster has a field of view slightly larger than a scope of normal length with the same specifications. But in my experience, the exit pupil is more critical on the Bug Buster. In other words, your eye has to be in exactly the right spot or you can’t see the image. That was how the scope acted in the test of the 3D bullpup, but I don’t know if it was the odd hold I had to use with that rifle or not.
The whole reason I’m testing this scope is because of the new, finer crosshairs. I guess the small groups I got in the test attest to the fact that these lines are thinner and thus better able to parse the bull closer. I don’t know of a more dramatic way of demonstrating it to you unless you look through the scope yourself.
And, of course, the thin inner crosshair lines have mil-dots running in both directions. So, you can estimate range if you read and apply the data in the handbook that comes with the scope.
I was concerned that because I’m colorblind, the illuminated crosshairs would be of limited use to me, but that isn’t the case. While many of the colors do look alike at the lower power levels, I can see differences in all the colors at the maximum intensity. The 2-button system takes some learning, but turning on and off are both simple commands, so there’s no danger of running down the battery. And there’s a timed shutoff, on top of everything. I don’t think I would use the illumination most of the time, but it’s there if you need it, and the battery will keep a long time if not in use.
On the highest power illumination, the inside of the scope tube gets illuminated some, as well as the reticle lines. Of course, the proper way to use this feature in the field is to run the lowest illumination that you can see, so this really isn’t a problem.
My shooting buddy, Otho, has eyes that cannot see through most scopes clearly even with corrective lenses. But all the Leapers models have a very extended eyepiece adjustment that suits him fine. When I sight through his scopes, I have to make gross adjustments to keep from seeing double reticle lines. Only the Leapers scopes have enough adjustment so that both of us can use the same scope.
Lockable reticle adjustments and adjustable zero
Back in the bad old days, we would adjust our reticles until they were perfect and then never let anyone near our guns. I’ve had people grab one of my airguns off my tables at a show and start twisting both adjustment knobs with abandon. When I asked them what they were trying to do, they said they didn’t know — they just wanted to see how the knobs felt!
Well, the Bug Buster’s knobs are locked in place with collars that screw down tight after adjustments have been completed. That gives me time to snatch my rifle back from someone before they can screw up my scope setting.
The scales on both adjustment knobs can be loosened and repositioned so your sight-in is shown as the zero point on each scale. Then, if you have to adjust the knob in the future, you always know where to return.
Below the scale of each adjustment knob is a thin collar that can be turned down to lock that knob from turning. This protects your scope adjustment. You can also loosen the small Allen screw on top of each cap and slip the scales to keep the settings as your zero point.
Flip-up scope caps not useful
The Bug Buster comes with flip-up scope caps that I find less than useful — especially on the objective lens. Since the AO requires the objective lens to twist, the flip-up cap is never in the right position and will just get in the way. I take both scope caps off when using this scope because I can’t be bothered with them. If the AO were a sidewheel, then flip-ups would make a lot more sense to me.
The Bug Buster is a compact scope. As such, the scope tube sections where the scope rings attach are very short. So the rings have to move to where the scope needs them to be, because there isn’t a lot of extra scope tube on either side of each ring. A one-piece mount is all but impossible to use, as the location of the rings would only line up with the scope tube by coincidence.
Many airguns do not permit a scope to be mounted far enough to the rear for the eye-relief to work with a short scope like this. You have to consider that when mounting a Bug Buster or any compact scope. If the gun has a scope stop plate or vertical stop hole located far forward, it probably will not work with a Bug Buster. But if the top of the gun is wide open, like on the Rainstorm 3D bullpup, then it’s what you want.
The new 3-9X32 AO Bug Buster is the best one of the entire line. It offers more flexibility, yet comes in the same compact package as all the other Bug Busters. It meets a specific need in the scope world, yet still provides enough flexibility to work on many airguns.