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Variable scopes

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BEAR View Drop Down
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    Posted: 19 December 2017 at 01:56
Seems most people us variable scopes, the 3-9x being the most popular.

Do you think  your POI changes with increased/decreased power setting?

If you sight in at 9x, will the same sightin be good at 3 x?

I've been sighting in at 9x but shoot most game at lower power range.  Should I sight in at 4x??????


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Post Options Post Options   Thanks (0) Thanks(0)   Quote jsgbearpaws1 Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2017 at 03:36
Sometimes it does enough to matter, most times not.

Eric Poole for G&A wrote a nice article a couple years back on that exact topic. Seems like it happens to even the best of optics and occasionally a cheap optic has none. Has a lot to do with focal plane and the movement thereof. Burris made a huge deal about it as I recall when they launched their newest offerings, toting less shift then other makers to help with poor sales. In most field conditions on big game I seriously doubt it would even be noticed. LR paper punchers like to whine even when they realistically have nothing to whine about as their rigs are always cranked up. Varmint rigs are the ones it's a huge deal for as game is small and can be at your feet or 500+ and having to know what your scope is doing is a touch more....noticeable.

A fella I work with is regularly competing in LR open class with a full blown 6.5x 284 and has it topped with a big Swarovski. It's always at max setting for paper punchin, but he actually hunts with the 20 pounder and has the low end doped for just such a use. Even though the shift is barely noticeable, he's a big enough freak to worry about a 2" shift lower and left from the low and it arcs back up as he cranks it, but that's at 200 yards.......like that actually matters on the vital size for deer.....not! I have one Nikon that does the same at about an inch and it will never get shot by me past 200 so it's not a concern. My sons Leo has no discernable move that we have noticed nor does his new Monarch. My ATN has zero movement as the focal plane never moves. Haven't worked out if the vortex does or not yet but if id does, I doubt it would realistically matter in the field.
...oh yeah! thats gonna hurt!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote d4570 Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2017 at 11:31
Yes , yes it does.
On my 45/70 I have a Cabela's leveraction scope 3x9.
It's made for a 45/70 shooting Evolution bullets, 350 gr. gummy tips.
Which my gun will not shoot, more like a shotgun pattern than a group.
Back to the scope.
I have to shoot what I sight in. I use 6x.
Zero at 100 yards, If I move up to 9X it is Zero at 200 yards.
If I drop down to 3x it is Zero at 50.
With all that said;
If I'm zero at 100 on 6, and change to 9X I'm 4" high at zero.
To make things more challenging.
The gun shoots 5" high with a cold barrel , clean or fouled .
On the money shot you shoot high, So I sight it in Cold, half hour between shots on 6X. It will shoot 1" groups with my Hornady 300 hp. bullets at 2500 fps. It is even a little better with a Barnes 250 at 2600 fps but I feel I need more metal.
My Redfield's and Leopold's shoot the same at any and all powers.
Does all that make any sense ?
 
 
 


Edited by d4570 - 19 December 2017 at 11:33
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RobertMT Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2017 at 13:14
D4570 it sounds like your Cabela's scope is second focal plane scope. Because the reticle stays the same apparent size, as background image's apparent size changes, as power increase. The center of reticle shouldn't change, but the reference marks do, if the reticle is not centered in scope, even center cross will change.

As far as scope changing POI, with power change, the parallax is the cause. On a 3x9 without parallax adjustment (most don't) the scope maker has to pick where to set parallax at, both @ what range and power, most times centerfire scopes are set for 100yds and 6X (middle of power range). Rimfire scopes are normally set for 50yds, muzzleloader and slug scopes for 75yds.

With some 10x and most above that, parallax adjustment takes care of the shift. The larger the objective lens, smaller the tube and higher the magnification, the more POI will shift due to parallax. Of course some mechanical shift due to tolerances, can occur, but on all but the cheapest scopes, that shouldn't be issue.

For a 3-9x 40mm scope, I would go ahead and sight it at 6x and 100yds and verify it at both 3x and 9x @ 300yds. 300yds is far enough to notice any shift and close enough to get decent group @3x.

While you'll see some LR target scopes, with variable power, you won't see many change powers, during string. They change scope power for conditions and verify zero, before shooting for score.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote d4570 Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2017 at 14:20
YUP.
 To much thinking for me so I shoot one bullet to kill and leave it at 6X...Sleepy
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BEAR Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2017 at 07:27
WOW, that is the most challenging rifle I've ever heard of.

Thinking I'd have to do the same, 6x always.

That is one of the problems with buying Cabela's stuff; you don't know who made it.  But they seem to take bck anything.  That may change now that they are BassPro.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BEAR Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2017 at 07:31
Yesterday I went to the range to check the zero on my 22 rf.  And took the opportunity to check it's zero as I ran from 4x up to 16x.  Scope is a Weaver Grand Slam, on my CZ 452 FS.  Groups were identical thru the x range,     .45".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RobertMT Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2017 at 11:29
Because parallax is set @100yds, by most mfgs, you need to shoot that CZ @300yds, to see measurable changes, due to parallax.    You might also see it at 150yds or 50yds.

I have half a dozen Weaver scopes and they all seem to track well. They're at the high end of what I'll pay for scope, but value is there.

I've only bought one Cabela's scope or for that matter one of outdoor life's recommended "best buy" scopes, I've never trusted either's brand nor recommendation again.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BEAR Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2017 at 12:15
Cabela's is todays Herter's  they just have an electronic catalog!  I do have a bunch of Herter's catalogs; reading them was the best part of that business.

Neither made stuff just bought lowest cost supplier, clones of top of the line things.  Both claimed there stuff was world renound and perfect!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BEAR Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2017 at 12:18
My Weaver has focus and parallax adjustments.

Do you think that change of scope sight-in with power change is a parrallax issue?

I thought it was an issue with the erector tube rails/tracking.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RobertMT Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2017 at 12:47
On the earliest variable scopes, that was definitely an issue, but has been largely fixed, some mechanical shift due to tolerances, can occur, but on all but the cheapest scopes, that shouldn't be issue.

Most of the shift in todays scope, other than the $50 specials, is due more to parallax, than mechanicals of changing magnification, parallax focus changes with magnification change, it's just small enough, in lower powered scopes, not to have large effect.

Where it matters, even very low powered variable scopes have parallax adjustment. https://www.ssusa.org/articles/2017/10/17/preview-hi-lux-xtc-1-4x34-mm-service-rifle-scope


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