I don't understand the question. I wrote this myself from stuff I know and can calculate. I'm happy to be corrected on anything.
Just wanted to say thank you to Nikonuser for his explaination. I found it very informative and easy to read. Having just gone through the purchase of my first scope, I was glad to realize that I had interpreted what I was seeing on the manufacturers websites correctly (and my fnal descision wasn't bad). Knowing how the scope actually works is very useful.
nothing to correct,
It's not uncommon for members to cut and paste from other websites,
I was just wondering , in case there were for more pages of valuable info , elsewhere
Safety, Situational Awareness and proficiency.
Neck Ties, Hats and ammo brass, Never ,ever touch'em w/o asking first
I have seen some of these topics discussed in other venues, but not in the breadth and detail that NikonUser went to the trouble of explaining. Sometimes the detail is there, but the focus (NPI) is much narrower. At one time Leupold had an explanation of the “optical triangle” that discussed (IIRC) the relationship among magnification, eye relief, and field of view. Unfortunately, many people don’t have the patience to read a detailed discussion no matter how well written.
Yeah, I get that. Sorry to disappoint, it's all my stuff and all errors are mine and I'm happy to be corrected.
Now, let's talk canted rail.
As we discussed earlier, a 1 inch tube will have a total adjustment range of between say 35 and 50MOA, the 30mm scopes are about double that. Some are even wider, I have an old Nikon Tactical with a 30mm tube and 80MOA adjustments. I've seen higher even.
So let's take a scope that has 45 MOA of maximum adjustment. What that means is that between the bottom adjustment to the top adjustment, there is about 45MOA of adjustment. Given a receiver and a scope mounting system that is perfect, the scope at its mechanical 0 is perfectly parallel to the bore of the barrel; both the barrel and the crosshairs are on the same target, with the difference being the distance between the bore and the middle of the scope.
At that setting, your scope now has 22.5MOA of up elevation available and 22.5MOA of down elevation.
In order to zero the scope at 100 yards, you will probably have to add a couple MOAs of up elevation. If you want to zero at 200 or 300 yards, you will need to add more up elevation, and any ballistics calculator will show you the come-ups for the various distances. To get to those distance, just dial in the come ups that you have calculated. Easy peasy.
But as you approach 22MOA of up elevation, the reticle stops moving up and doesn't got left or right worth a darn either. You've reached the maximum travel.
The problem is that before you can zero at 100, half the adjustment range is useless to you, the bottom half. Enter the canted rail. Some people think that a 20MOA canted rail will give them 20MOA more adjustment range. Not quite. What a canted rail does is it forces you to start using the bottom half of the scope's adjustment range by making the scope at mechanical zero with the perfect setup discussed above, point 20 MOA below the bore of the barrel.
To counteract that and make the crosshair and the bore be at the same point on the target. That means that when everything is parallel once again, you have 42.5 (20+22.5)MOA of up elevation and 2.5 (22-20.5)MOA of down elevation. You still have only 45MOA of elevation, but it's now divided differently between up and down.
42.5MOA of up elevation will allow you to reach out quite far with a .308 or any of the other long range loadings you might contemplate.
Canted rails comes in different angles, I've see 10, 20 and 30MOA rails. I'm sure there are more. Be careful of too much cant as it may prevent you from getting a zero at 100 yards.
Also remember when I said "perfect receiver and mounting system," it doesn't take much to misalign these things and then you end up eating some MOA range just because of imperfect hardware.
Some of you may think "why don't I just get a 20MOA ramp for all my rifles, even those I only shoot at 100 yards?" This is not a bad thought and in fact most of my rifles have a 20MOA mounting system of some kind. But they are zeroed at 300 to 1000 yards. The ones I never shoot farther than 200yards have no such device. There is no need to compress the scope's inner adjustment springs or having it push the inner tube right next to the scope's outer tube; having the scope's inner tube right at the inside of the outer tube inside diameter, may impede the windage travel.
Note: you can achieve similar results with the Burris Signature rings with their various inserts. Push the rear up and lower the front. It's more complex and you have to take the distance between the front ring and the rear ring into consideration.
Yeah, I'm trying not to get too technical and I'm trying to cover all things related to scope selection and understanding of the various components as they all relate to shooting.
I know a great deal about long range and precision shooting, but I don't know anything about QCB, holographic sights and all that jazz, so I welcome others to fill in those big areas.
BTW, I just received a couple new gadgets for my March-X. A lever for the zoom adjustment ring and a bigger wheel for the side focus. Both devices make it easier to adjust.This message has been edited. Last edited by: NikonUser,
Nikonuser, I just wanted to say great job on your write-ups. Informative and to the point. If you haven't already, take a look at Nikon's new Black Series. The entire line was built around spec's that shooter's have been requesting from Nikon for the last 2 years. MOA/MRAD,30 mm tube,Illuminated reticle and priced right.
Nikon Pro Staff
Bart940, thank you for the kind words.
I am aware of the Black Series and I think it's an awesome family of scopes for just the reasons you stated. Definitely something to look at for many of the folks haunting this forum; it fits well with their avocation.
In my case, the Black series is not something that interests me for multiple reasons. The big 60 is already several years in my rearview mirror and I enjoy much more sedate shooting venues (F-Class is really good for me.) The current magnification is not high enough for my needs, it doesn't have ED glass and the reticles are much more for PRS and other, more active engagements.
I will say this however, this is a great time in the riflescope world; new models with great features are coming out at a fierce rate and prices are dropping.
When earlier in this thread I said that the mantra "buy once, cry once" was for children, I really meant it. As a rule of thumb, you can see and feel the difference between a $100 and a $500 scope but it gets more difficult to see the difference between a $500 scope and a $1000. And then it gets extremely difficult to see the next difference and to justify the money.
So unless you need something really special, like a wide zoom range or being able to hunt at midnight, spending over $1000 or even $500 on a scope when you're not a "professional" (and you'll probably be issued a scope) or a hardcore competitor (in which case, you know exactly what you need and why,) is really not worth it. Something better will be along in a year or two.
Yes this should be a sticky!
I like the reference to the "buy once, cry once"! Years ago I was tasked with assisting Owners/Managers who were inputing physical inventory into a computer database. I noticed that the "high end" items had the same wholesale cost as the "low end" items which came from the same manufacturer. The retail cost was many times more for the "high end" items. When I inquired about the difference in retail cost, I was informed that the purchasers wanted the higher retail cost in the belief they were getting a better product. Think about the current wave of recalls for products today! Retail cost is not an indication of quality! How about those first handheld calculators?
Thanks NikonUser for the great information!
On the inside looking out, but not to the west, it's the PRK and its minions!
You're very welcome.
But let's make sure we're all on the same page here. In optics, price does make a difference in the quality of the riflescope. In my OP, I broke down the various components that contribute to cost and for some vendors, the NAME on the scope is a significant cost. There are only a few factories that make glass and multicoating such requires some pretty expensive devices and an environment to match. We're not talking about a spray paint job here. And assembling these riflescopes, especially as they get higher in specs and range, requires skill and equipment. So yeah, more money will get you better quality in optics, but at some point, it becomes very difficult to really see and appreciate the difference and each increment in quality costs a lot more money.
When looking to add a riflescope on a rifle intended for long range, we need to consider several thing but a main determinant is the size of the objective lens. Lots of people want to mount a scope as low as possible over the barrel, for some unknown reason, but to me the important aspect for the height is the comfort of the shooter. The actual height above bore is not important, you just need to know it and use it in the ballistics program. There is NO real benefit to having the scope mounted as low as possible in a long range rig and it's debatable whether there is any in short range rifles.
What you need to figure out is where your eye will be above the receiver when you are comfortably in your position, and also the shape of your face (where is that cheekbone?) Getting a good repeatable and comfortable cheekweld is crucial. With an AR, it is recommended that your face have a chipmunk look when looking through the sights. Ok, but with a riflescope it could be a little different. Remember, comfort and repeatability are key.
If your rifle has an adjustable cheekpiece you have a lot more flexibility to adjust it for you, a "Monte Carlo" stock is also a way to get some proper cheekweld for a scope, because some factory rifles have stocks with a comb that drops off whereas others have straight combs.
I shoot long range from prone, not seated at a bench. I spend a lot of time looking through the riflescope and the spotting scope, so comfort is key for me. Also, I have a long face and I'm quite tall. I keep my head vertical so as to not induce neck fatigue. Spend some time behind the rifle and find where your eye should be for the most comfort. Have someone measure how high from the comb or the bore line your eye is. With either of those measures, figure out how high the centerline of the scope needs to be.
Now that you know where you need the centerline to be, let's make sure it's not too low. On most scopes, the objective bell will be the widest part, at the front of the riflescope. You know the size of the objective lens, add 6mm to get the filter size (something else I'll talk about later,) and usually 2mm more for the OD of the bell. So my 56mm scope has a 62mm filter size and a 64mm OD. This means that the centerline of the scope needs to be above 32mm to clear the receiver. If there are further high points above the receiver that will be near the objective bell, you need to account for those as well.
Dimensions for the rings are usually available at the website of the ring manufacturer, but those will usually be in inches. For a 56mm bell, you need the middle of the right to be greater than 32mm or 1.26inch. Rings will usually come in factors of 1/8 (.125) inch and if you have a Picatinny rail, that distance will be from the top of the rail to the middle of the ring. They can start anywhere from .750or similar and go up from there. So, 1.00 inch then 1.125 then 1.250 and so on. Looking at the Burris optics site in their XTR series, the 34mm rings come in 1.00 and 1.50 inch. Remember this is measured from the top of the rail, but you need to verify this with the vendor.
When buying rings, you need to know the diameter of the main tube so that you don't end up ordering the wrong size; never try to fit a 30mm tube in an inch ring. There are many one piece scope mounts, some are QD, if that's important to you. Since we are talking long range here, regardless of the riflescope you've selected, you want to mount it with a minimum of 20MOA cant. We talked about the rails above, there are also one piece mounts that come with 20MOA cant built-in and there are also the Burris Signature rings with their inserts that can be used to create a cant with just the two rings and their inserts and nothing else. The only thing you need to take into account is the distance between the front and rear ring; that will influence the slope or cant.
Some people think they need to lap rings before mounting a scope; eschew that practice if you have a quality mount; there is nothing you can fix lapping by hand and much to screw up. When tightening the rings, use a torque screw or nut driver with inch/pounds measurements. Read the recommended torque values from the mount manufacturer. Usually, the screws for the rings holding the scope will be in the 15-30 inch/lb range, but you can really screw down the screws holding the rings to the rail or receiver (50-60 inch/lbs).
Avoid having the rings close to or at the knobs bump in the middle of the scope or right at the ocular.
|Go ahead punk, make my day|
Thanks for the original thoughts gleaned from your experience / knowledge. Much appreciated!
I believe a case can be made in some situations for mounting a scope as low and as close to the bore as possible.
Combat and hunting rifles are often used to engage short range targets under conditions in which speed is of the absolute essence. I believe low sights help with that speed goal. Before optical sights became common, iron sights on hunting and combat weapons were always as low as practicable, and the stocks were designed accordingly. The most extreme example is the simple shotgun sight used by generations of hunters and clay target shooters. The rear “sight” is a shallow groove or mark in the receiver and the front is a small bead attached directly to the top of the barrel. Part of the reason for low sights on such guns is reduce their susceptibility to damage, but any cant or tipping of the gun causes less of a point of impact shift. It’s also vital that the stock be designed to accommodate a high head position; one of the essentials for a good, consistent shooting position is a consistent cheek weld (what we referred as “stock weld” decades ago). If the head must be held too high to achieve that consistent head positioning, practical accuracy will suffer. With a scope sight mounted on my M1A rifle, I must add over an inch and a half of stock riser for a proper cheek weld.
I understand the advantage of mounting a sight as high as necessary on a competition gun. A more upright head position causes less strain when firing long strings and in certain shooting positions. The iron sights I have for my Winchester model 52 target rifle mount much higher than those on my Ruger 10/22. I don’t, however, believe we can say that a low sight mount is always counterproductive or of no value.
I get what you are saying. 3 points.
1- I draw your attention to the AR-15 design where even the iron sight is quite high by design and I think that rifle is used in the various engagements you describe.
2- My arguments are about scoped rifles mainly used at long range, but I still think it's counterproductive to scrounch behind a riflescope to shoot at close range.
3- I never proclaimed to know anything about combat, or military doctrine in anything. I should think however, that if one is going into combat one will be issued a weapon; I don't think you can bring your own.
Just adding to the discussion for a different perspective on a specific point, not criticizing anything you said.
As for the AR-15 that I do have a lot of experience with in close range shooting, your point is absolutely valid: It and its variants are the most common combat weapon in the US and many other countries, so how can high sights be bad? I would submit that people get good with the gun because they have no choice, not because it’s the best design. Although it’s been decades since I trained extensively with the M14, I still prefer that design when using iron sights over the AR type rifle—but not when using optics. The M14 is even less suitable for fast engagements when an optical sight is mounted.
Although Jeff Cooper and I didn’t agree on everything, he too preferred a hunting type stock with a very low mount scope on his “scout” rifle for fast, close-distance engagements.
Different perspective is great. Always welcome.
Even if it's wrong. (Ducking for cover.)
With some chassis/stocks there is definitely a benefit to having the rings as low as possible as long as proper cheek height can be established. The average shooter probably does not have a adjustable height rear pad on the their chassis/stock to compensate for high rings. With the rings too high while shooting prone, possibility the shooter will be "climbing" over their rear stock making it very difficult to properly control recoil. It's my experience the lower I can get myself to the bore line, easier to control recoil, spot my own hits/misses.
I hear what you are saying and I'm sure there are stocks where the setup calls for the scope to be low to the bore.
That said, my point is that if the ONLY reason you're putting the scopes low to the bore, to the detriment of shooter comfort, you're doing it wrong.
If you can get it low to the bore AND maintain shooter comfort, that's different.
F-TR is all about long viewing through a riflescope and controlling the recoil. If you can't control the recoil or you're not comfortable behind the scope, you'll struggle. If you experience both conditions, take up golf or Bullseye shooting.
|Get busy living|
or get busy dying!
A very informative read, thank you NikonUser!
As to some of the other discussions about use/suitability/budget......
Is the scope that came with my Rem 700 package enough to shoot 1,000 yards with? I got it for a steal, $575 at Dicks!
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