Basic magnification questions

[cowboybart]

I am not a competitive benchrest shooter. I shoot (off of a bench) for fun and to develop/test my skills.
I'm shopping for a scope for a 30" 6.5 RUM that I recently finished the metal work on. I plan on shooting it long range (1500+ yds), but am confused on the magnification of scope I will need. I was looking at the 8-32 NF, but I see a lot of people using the 12-42. Currently my biggest scope on a heavy gun stops at 20X. This seems to work for me to 1000 yds. Other that plinking at rocks, I have never shot at a target further than 1000yds. On lighter weight guns I have a 21x and a 24x. Once I get past 18x I see my pulse in these scopes. On a heavy RUM I don't want to see my pulse at 32x. How heavy does a person have to make a rifle to not see it at 55x or 60x??? What about mirage?? Won't that get exaggerated at 40x vs 30x?? If I put a 42x or 55x on top of this rifle, how often will I actually be able to go up to the max magnification??

Explain to me why a person shooting a 6BR would need a 42x scope? Is this just a competition thing? What type of event needs a 600 yd target magnified 42 times?? What am I missing??

 

[dkhunt14]

If you are seeing your pulse in the scope, somethings wrong with your setup. At 600 yards they are trying to put shots in the x ring. They are also trying to shoot very small groups. Matt

 

[Turbulent Turtle]

It really all depends on the target size and how precise you have to be in order to make a difference.

You stated that you are not a competitor, so I would think that whatever you set as your goal is what you need to gear up for.

And as DuckHunt14 said, if you detect your pulse in your scope, you are doing something wrong. I run my F-TR rig at 40X and 50X depending on the conditions and I never detect my pulse in the scope and I can hold the rifle on target for as long as I need. I am not special, every other F-class shooter worth anything has no issue with pulse in the scope. You learn to deal with it early on and it disappears.

The reason F-class shooters favor high magnification is because they want to surgically place their shots and the rings are small.

 

[Zero333]

The fella who won this years King of 2 Miles ( and hit the target at 2 miles on his 3rd shot ), I read he used the Nightforce 7-35 x 56.

Someone correct me if I'm wrong.

 

[Depart123]

If you are just looking for hits on a steel chest size plate, 20x is plenty out to 1500yds. I've done it with 16x but it is a little small. Depends on the width of the crosshair also. I've heard more than a few PRS guys say they spend the most time between 12x and 18x on thier FFP scopes. To each his own.

 

[Rob01]

You need to worry more about the internal elevation on the scope than the max magnification if shooting ELR as you will run out of elevation in some scopes. Most forget they need to not only see the target but dial to hit it too. You will want a scope with at least 100 MOA of total elevation so you can use a base with 20-40 MOA and still get plenty of elevation.

As for magnification, I have shot on MOA targets to 2500 yards on 17x and had no issue seeing the target. Something with a top 25-30x would work just fine for you. As PRS was mentioned and that is my main sport I will agree that I spend most of my time around 12-16x in that sport for shots out to 1300 yards. Other sports like mentioned have small X rings and small elevation and windage adjustments to get as close to center as possible. All about the game you are playing.

 

[cowboybart]

When NF or Leupold or March say 60 MOA elevation, is that 60 above and 60 below the mechanical center or is it 60 total (30 above and 30 below)??

I don't think I've ever seen more than 80 MOA of elevation is the scopes I am looking at. Maybe I am looking at the wrong scopes.

 

[Rob01]

60 total. 30 up and 30 down. That is why people use 20 moa bases to make that 50 up and 10 down.

Usually the higher the magnification the lower the travel will get but not always. A 5-25 range is usually a good area to get 100+ moa and good magnification range.

 

[Turbulent Turtle]

Well, actually the adjustment range of a scope is more of a function of the diameter of the main tube as well as the focal length of the objective lens. I've noticed that some manufacturers of 34mm main tubes chose to use the extra 4mm increasing the thickness of the main tube as opposed to providing more adjustment range or a larger inner tube with bigger internal lenses. For instance, my March-X has a 34mm tube but the thickness of the tube material is 4mm as opposed to the regular 2mm used in 30mm tubes (and probably 1inch tubes as well.) That does make for one very strong tube but I can't help but wonder if it could have been a 3mm thickness and use the remaining 2mm for added adjustment.

 

[Rob01]

True to a point as well but I know 1" scope that has 100 moa of adjustment and 30mm with 45 moa. There are a lot of variable in magnification and scope design.

 

[Turbulent Turtle]

I would love to see that odd duck. Brand and model, please. Or it doesn't exit.

 

[dkhunt14]

What about the original Mark 4 with 140 minutes. Matt

 

[R.Morehouse]

Well, actually the adjustment range of a scope is more of a function of the diameter of the main tube as well as the focal length of the objective lens. I've noticed that some manufacturers of 34mm main tubes chose to use the extra 4mm increasing the thickness of the main tube as opposed to providing more adjustment range or a larger inner tube with bigger internal lenses. For instance, my March-X has a 34mm tube but the thickness of the tube material is 4mm as opposed to the regular 2mm used in 30mm tubes (and probably 1inch tubes as well.) That does make for one very strong tube but I can't help but wonder if it could have been a 3mm thickness and use the remaining 2mm for added adjustment.

I have the March X 8-80x56 with a 34mm tube and 60ele 40wind. It weighs 29.8oz......The NF Comp. 15-55x52 with a 30mm tube, 55ele & 50wind comes in at 27.87oz. Can't imagine the larger March is carrying much more weight in a thicker tube being only 2oz- heavier than the Comp. that is a full 8oz. lighter than the N.F. 12-42x56 BR..............

 

[Rob01]

I would love to see that odd duck. Brand and model, please. Or it doesn't exit.

My mistake. It's only 80 in the 1 inch tube. I had ones years ago and was surprised at the elevation amount from the 1" tube.

https://www.midwayusa.com/product/9...mm-1-10-mil-adjustments-mil-dot-reticle-matte

 

[Rob01]

What about the original Mark 4 with 140 minutes. Matt

Yup the 16x

https://www.leupold.com/scopes/rifle-scopes/mark-4-lr-t-16x40mm

 

[Turbulent Turtle]

My mistake. It's only 80 in the 1 inch tube. I had ones years ago and was surprised at the elevation amount from the 1" tube.

https://www.midwayusa.com/product/9...mm-1-10-mil-adjustments-mil-dot-reticle-matte

You have to help me out here; I'm old(ish) and easely confused, The link you provided talks about a scope with a tube diameter of 1.18 inch, which I take to be 30mm. (Hey, I'm an American, I don't do metric.)

BTW, did you know there are two kinds of countries? Those that use the metric system and those that went to the Moon and back.

In the specs, they mention 140MOA of elevation and 45MOA of windage. If it's on the Internet, it must be true.

Now, where is the 1inch tube equivalent?

(And I am laughing, they call this an LR (long range) scope, 16X40.)

 

[Rob01]

In my first post I linked the scope that is a 1" tube. The one you quoted. The second post is the Leupold that someone else mentioned. Look again at the midway link. 1" tube.

 

[Turbulent Turtle]

Ok. I completely misunderstood your earlier posting. I though you were talking about a scope from a single manufacturer that was offered on a 1" tube with 100MOA of adjustment as well as 30mm tube where it only had 45MOA of adjustments. Now I see you're talking about two completely different scopes from different manufacturers.

The 30mm tube is the Leupold Mark 4 LR/T 16X40mm which the Leupold website says it has 140MOA of elevation and 45MOA of windage.

The other one to which you linked is the Bushnell Elite 3200 10X40 with a 1" tube and 80MOA of elevation.

I am not familiar with either one, but I notice the strange configuration of the Leupold and the huge difference between elevation and windage range. If the numbers are indeed correct, I wonder if they might have made the inner tube with very little material on the top and bottom, leaving the sides with more meat to hold the thing together. It could also be in the placement of the springs and that may explain the strange configuration.

In either of these scopes however, the manufacturer may well be using smaller lenses in the inner tube in order to get a larger range of adjustments. When you get a chance, can you take your apart and measure the inner tube for us?


The thing of it is, the tube diameter dictates the field of view and the magnification of the image at the first focal point, the one at which the inner tube looks. Most of the magnification in a scope and certainly all the zoom is accomplished after that first focal point and all that will not have an impact on how much the inner tube moves and by extension, the adjustment range.

This is why the range of adjustment stays the same in my March-X from 5X to 50X and in R.Morehouse's March-X from 8X to 80X and it's the same range for both scopes, because the objective lens is the same and the focal length to the first focal plane is the same. The additional 3X of magnification in the 8-80 is accomplished in the inner tube, and does not affect the adjustment range.

One way to increase the adjustment range is to reduce the focal length to the first focal plane, thus creating more of a wide angle image and then increase the magnification after that first focal length. The problem with that is that you use a smaller objective thus reducing the amount of light coming into the scope while increasing the amount of distortion at the FFP. So the perspective at the FFP would have smaller objects in a wider FOV and that would provide you with a lot of adjustment using regular size inner tubes. Everything is a trade-off in optics.

Just thinking out loud here.

 

[cowboybart]

Now my head is really hurting!

 

[Rob01]

The first post was for you and the second was for the gentleman who mentioned the Leupold. Not very confusing. Two different scopes. Two different links.

I am well aware of how scopes work. Not new in the sport or shooting precision rifles but good info for those that don't.