Value of an Adjustable Objective

[inthebeech]

I bought an old Weaver V9 just to get my feet wet with minimal investment and see for myself just how useful they would be to me (Preliminary findings are that I do like what they give you).  I am currently comparing its behavior with a non AO 3-9x that I also have.

What I don't understand is the apparent difference in the way two identically powered scopes behave.  When the AO scope is all set up at 100yds and then I choose a second target at 50 yards (power setting held constant), I MUST readjust the AO (by refocusing at that shorter distance).  With a non AO scope the image is still sharp; albeit I am now getting the typical movement of the image relative to the crosshairs which is what the AO scope eliminates, but it is not REQUIRED that I refocus.  So am I correct in this basic trade off?   I was not aware that the adjustment of the objective is actually NECESSARY when you move the gun among targets at various ranges. 

This makes me rethink my decision to use an AO scope in the field.  If a squirrel's image is going to get blurry as I track it running away (or towards me) and I must refocus with the AO ring, I may want to stay with the lower powered, non AO scopes.  My goal here was to eliminate the variability of POI due to the two common circumstances encountered in the field; these are the slight positioning errors of my head on the stock which happens when trying to get yourself in some sort of reasonably stable shooting position, as well as the range to your target being something different than that in which your scope is parallax free.  Comments?

[mcwoodduck]

I have a couple rifles that wear Adjustable Objective front ends.
One is a Pellet rifle - Gamo .177 Later replaced with a fixed ojective.
Second is a varmint rifle Rem 700 SPS in 223
third is a Winchester 70 in 338 Win mag.
I find the AO to be slow.
But helps to define range, when it is clear you know how far and you can guess your bullet drop.
I went nuts with the 338 on my first Elk hunt going from trees to open fields and back into trees dialing the front of my scope.
I went so far as to buy a second rifle that had a fixed 4 power scope.
i can see with the Varmint rifle the advantage of a nice clear picture at given ranges on small targets.

[drdougrx]

I have quite a few...mostly 4x12 leupolds.  I set the AO on 100yards and leave it there unless I have time to adjust it.  I've never needed to change it really.  Most scope are set at 100 or 150yards internally anyway.

[parkergunshop]

I only have one scope with an adjustable objective.

A 24 power Leupold used for benchrest competition, the AO is good when you change from 100 Yds to 200 Yds or 300 Yds to get the clearest possible sight picture when you are shooting for the smallest group possible, a one hole group.   Here 1 thousandth of a inch can mean the difference in winning or losing, but for game of varmint shooting even 1/2 inch seldom makes a difference.

On a big game rifle they are just a nusance, as is changing power on a variable power scope.  I have 3x9 and 3x10 scopes but normally set them at about 4x as I seldom have game that waits on me to play with my scope settings.    When hunting from a tree stand I have the safety in the fire position for I lost the biggest deer I have ever seen while moving the safety to the fire position.

[PowPow]

I set my 6-18x40 AO scope on a low power and set the AO at 2/3 the length of the field I am hunting in.
I figure if something walks out in the closest 1/3 of the field, parallax won't really matter because its close; if something walks out in the middle or farthest third of the field, my worst parallax is a result of a 1/3 length-of-the-field error if I don't have time to adjust.
Don't know if that its the right thing to do, just seemed logical.

[drdougrx]

I agree with all the above.....currently I'm using AO's on a 17HMR (weaver 4x14AO), 22lr (weaver 3x9AO), an AR (Lpld 4x12AO), a 700 varminter (Lpld 6x18AO) and a 270 (Lpld 4x12AO).  Now that I think about it, the only one that actually gets used hunting is the 270 and I pretty much leave the power set at 4 or 6x and the AO at 100-150yrds.  I now use this for smaller big game such as pronghorns, etc.. where shots could be long.  The other rifles have pretty much been relegated to the range at this point.

[helotaxi]

Realize that while focus is part of the equation, parallax is the more important when you start talking about long range shooting.  AO and side focus scopes allow you to dial out parallax at a given distance and make the POA less sensitive to eye position. 

For a quick demonstration, put the rilfe in a rest so it won't move.  Set the parallax at around 75yds and look at a target at 100.  The focus won't be horrible and you might not even notice it at a glance.  Now look through the scope and without moving the rifle, move your head around behind the scope.  Notice that the crosshair moves in relation to the target as your eye moves.  Now adjust the parallax slowly toward 100yds until the crosshair no longer moves with your eye movement.  You'll probably find that the adjustment doesn't exactly correspond to your target distance and I wouldn't trust that as an estimation of range enough to base a holdover or comeup on it.

Lower magnification scopes are much more forgiving of parallax and are usually parallax free beyond a certain range (based on design purpose, i.e. 50yds on rimfire scopes and 25yds on airgun scopes).  Once you're over around 12x adjustable parallax becomes something of a requirement for accurate shooting.

[lilabner]

I use a 3X9 AO scope on my CS452 .22 long rifle. For hunting, I set it at the range most likely for a shot. There may be time to make an adjustment. Given the trajectory of the .22 LR, the AO feature is helpful.

[cwlongshot]

I love them on my rim-fires and Varmint rifles. The near elimination of parallax is the result when used on a firearm that's shot at varying distances.

I don't have any on regular hunting rifles.

CW

[Lloyd Smale]

i wouldnt buy a rimfire scope without it or another scope for a big game rifle over 9x without one. contrary to what some think your doing, all it does is focus your scope and at short or real long range or when a scope is cranked up past 9x you about need it. If you doubt it try to identical scopes one with it and one without it and youll be a believer.

[DannoBoone]

All my CF and muzzle loader rifles have AO scopes. Have been using them
since the late '60's, so using them has become second nature. When hunting,
it just seems natural for me to constantly adjust them for ranges where
deer may come into view. The newer side-focus versions are a LOT handier
to use than those on the end of the tube.

Might add, that all my deer hunting is still hunting or stand hunting, so in my
case, there's practically always time to adjust the AO. For others who do
different types of hunting, it may not be for them.