Home Forums Hunting & Shooting Hunting Optics AO versus non AO?

In laymans terms, what is the difference in an AO and NON AO scope. What are the practical differences in a hunting (deer) scope. Looking to get a 4.5X14X40 and want to make an informed decision.

Thanks, TM

When you change the position between your eye and the reticle, the image moves a bit. At short ranges, and with low powered scopes, this doesn't amount to much. Much beyond 300 yards and 10x, and it makes a difference. If you plan on hunting past about 300 yards, then I would get the AO on a scope of that magnification.

At closer ranges I still like a parallax adjustment above 10x, even if the visible parallax and less than perfect focus won't cause a miss on a deer.

Yes. The AO gives one the potential to dial out error at any range. It will also provide a crisp image at any range. If one wants to do nail driving shooting at short or long ranges with high power scopes it's a must.

If you own some scoped units, sit one on a stationary rest, pick a target at 30 yards and move your face from side to side and up and down while keeping the rifle study and cross hairs in view. The cross hairs will appear to move on the target. Now repeat the same exercise with a target at 600 to 800 yards. On most non adjustable centerfire grade scopes, one will experience zero parallax somewhere between 150 to 250 yards. It becomes more of an issue as magnification get higher.

I typically carry with parallax dialed out at about 250 yards for big game. Close in, the target is large enough that it doesn't matter. At extreme ranges, one will typically have time to dial it out.

If one has perfect technique and his eye is always aligned with the optical center of his scope, it's not an issue. That is not usually not the case though in a variety of field positions, and any scope I own over 8X will have some method of dealing with parallax. If one can afford it, and has the ability to dial out a source of error, he should take advantage of it.

I even have AO's on my lowly 22LR's. A half inch of error at 100 yards is more than enough to miss a ground squirrel. The same can be said for mouse sized baby ground squirrels at 20 yards.

I guess I'll be different.

I have AO on my higher powered target and groundhog scopes. High magnification and deliberate shots allow me to maximize the potential of AO.

On a deer rifle, nope. Just one more thing to screw around with. I think the longest shot I've ever made on a deer is 125-150 yards. It's just not a big enough factor for me to worry about at those ranges. Besides, the Leupold 2.5-8X that I use on about all of my big game rifles doesn't offer it anyway.

A 2.5X8 or 3X9 non-AO will handle 99% of any hunting situations.

To clarify, I killed 4 deer this year between 200 and 275 yards, including the best buck I have ever taken. Several places where I hunt offer shots of 300+ so looking to replace the 3.5X10 on my 257 WBY with a 4.5X14. With my almost 60 year old eyes, I think I could use just a little more help.

Thanks, TM

Substitute a 2x7 for either of them, and you've got it locked up.

I could happily use any of the three for all the rest of my big game hunting career, and be perfectly content.

I'll have to throw my hat in the ring with Coldbore and STARJCB. Lots of magnification and an AO are great on a varmint ( rodent type) rifle. On a hunting rifle I like less magnification, and the fewest bells and whistles possible. Just my opinion... Leupold was making a great 4.5-14 without AO for those wanting more magnification on a hunting rifle.( something I thought was long overdue, and was glad to see it.)
Where I hunt, the PDs and ground squirrels usually stand around for awhile while I dink with the bells and whistles,the deer...not so much...

AO usually adds some weight to a scope as well, whether or not that's significant...

Can't see using an AO for anything other than target/varmint work. Other than that they just add more parts. No trick to hit small things at distance with non AO scopes,IMO.

I believe you, but my answer was based on the original poster's declaration about getting a 4.5-14x40 scope. For me those have to be parallax adjustable.

At the range I can tear up a 3" sticker at 300 yards with a non-AO straight 6x on a bolt action 300 Savage sporter. If I can't make a shot at 300 on a deer with that rig it's my fault.

The reasons why Leupold makes it's 4.5-14X40/50 scopes with and w/o either an AO or a side focus parallax knob are two.
Scopes with such things are a bit more dim in the image. Might make a difference during low light situations. Frankly, I haven't noticed any realistic drawback here. I watched a very small forked horn buck once at 150 yds under a clear, moonless night for several minutes in spite of the AO on my 6.5-20X40AO scope. Could see the forks as he mingeled among the does, etc.
Scopes with such things have shorter depths of focus. Particularly those with the side focus/parrallax feature.
My custom gun maker insists that such scopes are prone to shift their zero more readily. I haven't seen that and some here couldn't duplicate this.
What is not true is that you need this feature for the best image focus. For image focus, you use the ocular to focus both the reticle and the image. At 10X, for instance, if focused for that range, my old VariXIII, set at 10X, can show me .30 bullet holes even in the black on a good day.
The other thing I've noticed is that if I focus the image for the longer ranges, I can reduce the parallax enough to shoot some very good groups. The above VariXIII sits on a Remington 700 VSFS. On the day it showed me those .30 bullet holes, those bullet holes were in a .87 inch group at that range.
If I insisted on the 4.5-14X40 for a big game rifle, I'd do it w/o the AO. Just something more to go wrong.
If it's for shooting small varmits, fine. Do it with the AO. E

I just love how people ignore your question, ignore what will satisfy you and preach you should use what they like instead.

You already use a 3.5-10X and have decided you want more power and have a question about the AO. Their answer? Get a 2.5-8X or a 2-7X because that's what they like! Gee, thanks guys.

To answer the question, AO/Sidefocus is somewhat a necessary evil on higher powered scopes. The higher the power the more necessary. There are a couple drawbacks, the main one you'll notice is the depth of field will be more shallow. This is only a problem on higher powers so if you're walking around with it on 4.5X or 6X, etc, it won't cause an issue. When you crank it up to 14X you may need to adjust it, depending upon distance so it can be an extra step (of course if you're in a hurry you don't need to crank it up in the first place).

Personally I wouldn't get a 14X without it. You can make do without if you want everything to be in focus all the time and a bit more simplicity, but it's enough power you will be compromising somewhere. Say if you have it set for 300 yds your long range accuracy should be fine but you may find it harder to shoot good groups at 100 yds. And visa versa. That may or may not bother you.

If you do much practicing at longer ranges (which I suggest if you're willing to do it hunting) it's very likely you will simply shoot better with a 14X AO, and that's what builds confidence which is a whole lot more important than most things in the equation. If you can do load development and group shooting at 300 yds and have no real need to shoot at 100 much, you might not miss the AO that much.

So it's really up to how you'll be using it the most, and what'll make you happy.

travelingman1,

I definately go for A.O. on everything. The idea that you fool with it is nonsence. When you go deer hunting, you set it for about 150 and leave it alone. Just forget it's there. Nothing to fool with.

If you have all the time in the world to take a shot at something on 14X, you will have all the time in the world to adjust the A.O. for the best shot. This puts everything in your favor that you can.

Whoops, sorry. I misunderstood the intent of the original post.

Yes, by all means, buy a 4.5-14X and definitely get it with AO. You will love it. It will do everything you could ever imagine. Other people's opinions don't matter. As a matter of fact, don't bother to ask. You MIGHT just get info that doesn't fit your pre-conceived and desired answers.

I mistakenly thought that he wanted input on whether AO was desirable or not on a deer hunting rifle. My opinion, which should never have factored into my answer, and allowed me to be biased in my narrow thoughts, was unnecessary.

If somebody wants others thoughts, ask, and you shall receive. If on the other hand, all you want is confirmation for something that you already have set in your mind, frame it differently, and don't allow the dirty masses to chime in.

AO is really nice on my 6x18 Loopy target scope. I wouldn't bother on a general-purpose hunting scope, myself... one more thing to go wrong... but they make 'em that way for a reason I guess. Someone must want 'em!

... should add, I donk my steel plates all day long out to 600 yards with 2.5x8 non-AO scopes. AO is cool, no 'bout adoubt it, but a little care with your head position and it's really much ado about nothing- IMHO- in a hunting scope out to reasonable ranges (say, 500 yards).

In a dedicated long-range rig, ABSOLUTELY go AO.

Careful there Jeff. That's two strikes. We're only talking 4.5-14X here.

It's all right, I'm pretty much always operating on 2 strikes around here, it seems ... grin...