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#69142 - 06/17/03 12:27 PM Advantages/Disadvantages of a scope with adjustable objective?
C5 Offline
Junior Member

Registered: 05/12/02
Posts: 47
I am not sure exactly what this means? I have been told I should get a scope that does not have adjustable objective for shooting closer than ~200 yards...

What is the difference between a scope than had AO and one that doesn't?
Thanks!!
Doug

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#69143 - 06/17/03 12:58 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
Anonymous
Unregistered


The adjustable objective allows focusing the scope to be free of parallax at various distances. Scopes without this feature are set at the factory to be parallax free at one particular distance - Leupold says they set their non-adjustable scopes for 150 yards.

There is no disadvantage to having a scope with adjustable parallax (assuming it's a quality unit). But depending on how you intend to use it, there may be no advantage to having it either. And if you won't be using the feature at all, it's kind of a waste to pay for it.

- DAA

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#69144 - 06/17/03 02:03 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
DaisyCutter Offline
Die Hard Member

Registered: 02/06/02
Posts: 738
Loc: AZ
I can attest that I've missed more than a couple shots at game because I was fiddling with an adjustable scope or cranked the mag. up way too high for a particular shot.

A couple years ago I used my dad's 1964 Model 70 .270 Featherweight on a whitetail hunt. It has a fixed 4x scope and I kinda liked the simplicity. It seemed adequate for anything in reasonable range for the rifle.

I'm not one of the buttheads that glasses game with a high power scope anyway. I use the binos for that.

Get what you like.

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#69145 - 06/17/03 05:27 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
Michael J. McCasland Offline
Retired PM Staff

Registered: 04/24/01
Posts: 9470
Loc: Tucson,Az
C5 - This is a carry over from another one of your threads, I thought that I'd try to answer it on the other thread but thought better of it.

scattergunner - If you've followed this thread over from the other thread, nice try but you missed the mark.

Daa pretty much hit the technical side of things. I'd like to make it simple.

An Adjustable Objective (AO) in the long run has nothing to do with the relative power or power setting of a given scope. You can find this feature on several tactical scopes that range in powers as low as 6x but in general you will not find AO on most scopes until the high end power reaches about 12x. Most lower powered scopes will not have an AO adjustment.

So what is AO. Have you ever looked into a scope and noticed that the cross hairs will jump around when you move your head around slightly on the stock while looking in your scope? If you have this is called parallax, the cross hairs are not opticly on the same plain as your target. Difficult concept I know, the same concept works for a survey instrument. Bacicly inaccuracies occure due to improper parallax adjustment. Properly adjusted cross hairs will not move on your target while moving your head slightly on the stock if parallax is adjusted properly.

Now for some of what DAA spoke about. Various scope manufacturers in non-AO scopes adjust to a parallax free conditions at certain distances, most center fire rifle scopes are set at 100 yards or a little more but never more than 200 yards (rim fire scopes are around 50 yards). This is the distance where most of us shoot. With very little variation this setting works very well especially if you have really good consistent mounting technique. The big bennifit in this type of scope is simplicity, you simply can't have youe scope set wrong.

Well then why a parallax adjustment?

It can be assumed that the higher powered scopes will be used at extended range where accuracy is much more important. In this case a parallax adjustment is important. Lots and lots of people think that a AO adjustment is there for to focus the scope and indeed you will find that focus is part of the equation, but the most important part of the equation is adjusting parallax out of your scope. As a matter of face your scope may not be at its sharpest image adjustment when the parallax is properly adjusted. Parallax is important for pin point accurate long range shooting. Now remove the bench from the equation and back track a little, off the bench and in the field it is the focusing factor that will get you in trouble most of the time with an AO scope.

How?

You are at the bench, the scope poweer is set at 14x, you are focused (and parallax free) on that 300 yard target and things are going better than expected so you jump up and run out to the field for a little calling. You sit down and absolutely fool a coyote almost into your lap, a 20 yard dead coyote so you draw down on the coyote to shoot but instead of the coyote you see nothing but hair, lots and lots of very very fuzzy hair, you have absolutely no idea if you are looking at your coyote or a dead tree. Then comes in the "Fiddle Factor" that we've all talked about. You've got to fiddle with your scope, not only turn the power down to a reasonable level but to adjust the focus (AO) ring so you have a clue as to what your looking at. Too much fiddling around and the coyote wanders off laughing at you. For the vast majority of shooting situations out to ~250 yards parallax adjustment is unecessary therefore the AO feature on most coyote hunting scopes are unnecessary.
_________________________
Michael
.....liars usually leave tracks, the trick is finding them without getting caught ......

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#69146 - 06/17/03 06:21 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
Anonymous
Unregistered


For the last 15 years or so, probably 95% of my calling has been with a scope equipped with parallax adjustment (AO). I've only very, very rarely had occasion to use the AO on a scope while coyote hunting. And it's always been when taking a very long range, very deliberate, very calculated shot. But, by the same token, I've never, ever, not once had the parallax adjustment hurt my chances of killing a coyote. Even if it were accidentally set for infinity, and a coyote popped up at 20 feet, it wouldn't make any difference - you'd still be able to obtain a useable sight picture and get the job done. The more common, more likely scenario of having parallax (AO) set for 400 - 500 yards, and a coyote that needs killing inside 50 yards, it just doesn't matter. It's happened to me a handful of times. Sure, the sight picture is a bit fuzzy, but not to where it has ever saved a coyotes life in my experience.

Anyway, I agree that AO isn't a feature you really need in a scope for coyote hunting. But it hasn't ever hurt me either - I sure wouldn't "disqualify" a scope just for having it. In fact, higher quality scopes in the magnification range I prefer pretty much all have parallax adjustment. To avoid it, in my case at least, would be to remove some darn good scopes from consideration.

Leaving the magnification cranked too high has in fact cost me one or two coyotes over the years. Or at least cost me the chance for a decent shot opportunity.

- DAA

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#69147 - 06/18/03 09:46 AM Re: Advantages/Disadvantages of a scope with adjustable objective?
scattergunner Offline
Die Hard Member

Registered: 07/16/02
Posts: 970
Loc: No. UT
Thanks for the clarification guys. I wondered if I wasn't unclear on the issue (pun intended ). I learn something new almost everyday in here.
_________________________
--Scattergunner WWJWD? - What Would John Wayne Do?

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#69148 - 06/18/03 10:14 AM Re: Advantages/Disadvantages of a scope with adjustable objective?
Iron Pony Offline
Die Hard Member

Registered: 03/28/03
Posts: 938
Loc: Post Oak Savannah,Greenville, ...
Michael makes a solid point and does from time to time. I always check my paralax before getting in the field especially after working the 300 plus stuff at the range. I've got a flip up scope cap (Uncle Mikes) that tells me when the AO is at 100 yds or not just from a quick glance at the scope from a distance. I can tell from the possition on the hinge on the scope cap, if the hinge is pointing directly up, It's 100 yds. I also carry a shell holder that slips over the stock made of neoprene so that I can grab the rifle without worying about grabbing ammo and the rifle is unloaded at all times reducing the likelyhood of misfire.

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#69149 - 06/18/03 10:22 AM Re: Advantages/Disadvantages of a scope with adjustable objective?
Michael J. McCasland Offline
Retired PM Staff

Registered: 04/24/01
Posts: 9470
Loc: Tucson,Az
Iron Pony - Thank you for sayin' that even I make solid points -from time to time-. But then again I hear that a stopped clock will show the correct time twice a day.

Excellent idea with the flip up scope covers, an instant point of reference, good one. That is is your AO turns the entire front of the scope. There are some models where the AO ring turns independently of the front of the scope, but still a great idea.
_________________________
Michael
.....liars usually leave tracks, the trick is finding them without getting caught ......

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#69150 - 06/18/03 12:40 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
AHunter Offline
Seasoned Member

Registered: 11/04/02
Posts: 412
Loc: Boise, Idaho
I have a 6 x 20 Leupold.
I set the Parallax at appx. 175 yards when big game hunting and 100 yards when coyote hunting.
Then I don't ever have to mess with it while hunting.
I have never missed an animal due to parallax problems or it being too out of focus due to the parallax setting or having to fool with my scope parallax settings while hunting.
It would have to be at extreme range before the animal would be too out of focus to take the shot with the setting set at 150.
Only time I actually set it at the exact yardage is at the range.

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#69151 - 06/18/03 04:06 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
Dakota Yote Offline
Seasoned Member

Registered: 01/28/02
Posts: 199
Loc: Bismarck, ND, USA
That is one of the reasons I like the side parallax adjustments on a couple of my scopes.

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#69152 - 06/18/03 04:12 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
Iron Pony Offline
Die Hard Member

Registered: 03/28/03
Posts: 938
Loc: Post Oak Savannah,Greenville, ...
Good stuff guys.

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#69153 - 06/18/03 08:00 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
Dr. Yotee Offline
Predator Master

Registered: 12/20/02
Posts: 74
Loc: Aberdeen SD
If the AO adjusts parallax, then why do some models have a parallax adjusting knob by the turrets?

I dont see why you would need to adjustments for the same thing?

I'm not saying anyone is wrong here, I just want to learn.

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#69154 - 06/18/03 08:16 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
Jack Roberts Offline
Former Admin/moderator - deceased

Registered: 05/10/01
Posts: 15854
Loc: Elko, NV formerly MD
Parallax adjustable scopes have one or the other not both. The side knob is much more convenient to use but normally quite a bit more expensive.

Jack
_________________________
"When the going gets tough, the tough get going."
"Yeah, to where the going's easier." Ben Bova

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#69155 - 06/18/03 08:21 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
Jack Roberts Offline
Former Admin/moderator - deceased

Registered: 05/10/01
Posts: 15854
Loc: Elko, NV formerly MD
Incidentally!
When adjusting the parallax on the bench, do not go by the numbers on the scope. They are almost invariably off at least some and frequently way off. Check for parallax by moving your eye while sighted on the target. Adjust to where there is no movement of the crosshairs.

Jack
_________________________
"When the going gets tough, the tough get going."
"Yeah, to where the going's easier." Ben Bova

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#69156 - 06/18/03 10:18 PM Re: Advantages/Disadvantages of a scope with adjustable objective?
C5 Offline
Junior Member

Registered: 05/12/02
Posts: 47
Thanks for the info guys, this site is awesome!!!

I am learning new things everyday!!

I think I will go with a nice quality 3x9 scope without AO, should do me well for an all around farm gun.

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