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Author Topic: Cant errors  (Read 36280 times - 2 votes) 
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Offline KW80

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Re: Cant errors
« Reply #60 on: December 31, 2017, 03:55:07 AM »
Hey guys....
Hope all of you are well.

Jes a request to Scotchmo and others.....if you could kindly upload the pics again using some other hosting site as the pics are no longer visible. I actually wanted to guide a friend abt scope cant and was thinking of forwarding him the link to this topic.

Regards.

SORRY GUYS, THERE WAS SOMETHING WRONG WITH MY SERVICE PROVIDER. IT'S ALL GOOD NOW.
« Last Edit: December 31, 2017, 06:38:55 AM by KW80 »
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Offline Relentless Holiday

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Best scope mounting post ever.... BTT This may even be sticky worthy!
« Reply #61 on: January 20, 2018, 12:14:31 AM »
Been shooting AG for about 20 yrs and finally found this site and this thread.

All questions answered at once.  Thought I was trying to learn how to move windage adjustable mounts into barrel alignment with a leveled gun reciever.   Nope.  That's bass ackwards...

But I do want to add to this by suggesting a great lil trick to assure scope mounts are worthy of the effort.

Saw it here on another thread, I take no credit:  Mount rings in opposite directions.  screws on opposite sides of the rail with the two rings touching to check them for centering on a rail.  Cheap mounts may not match up and require you to adjust farther to the edge of the optic center than good ones may.

This is by far the best scope mounting post I have ever seen on any BB...ever. Thanks to you all, even from way back when this started.  And yeah if anyone has those photos, this post is definitely worthy of the maintenance.

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Offline nervoustrigger

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Re: Best scope mounting post ever.... BTT This may even be sticky worthy!
« Reply #62 on: January 20, 2018, 12:21:57 AM »
Saw it here on another thread, I take no credit:  Mount rings in opposite directions.  screws on opposite sides of the rail with the two rings touching to check them for centering on a rail.  Cheap mounts may not match up and require you to adjust farther to the edge of the optic center than good ones may.

Actually, it is of no particular importance that the mounts be perfectly centered over the dovetail.  Your scope can be offset to one side, then you simply rotate it to align its reticle with the bore before you tighten it down.  From that point forward, when you shoot, so long as you hold the reticle level, the pellet will rise and fall in line with the reticle.
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Offline rsterne

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Re: Cant errors
« Reply #63 on: January 20, 2018, 01:25:56 AM »
I can pretty much guarantee that MOST mounts will not line up, if you fit them with screws on alternate sides.... if for no other reason than there is little standardization on dovetail widths on airguns.... As Jason said, a slight offset is not an issue, as long as the vertical crosshair bisects the boreline....

Bob
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Offline Relentless Holiday

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Re: Cant errors
« Reply #64 on: January 22, 2018, 12:35:00 PM »
I can pretty much guarantee that MOST mounts will not line up, if you fit them with screws on alternate sides.... if for no other reason than there is little standardization on dovetail widths on airguns.... As Jason said, a slight offset is not an issue, as long as the vertical crosshair bisects the boreline....

Bob

Now I feel really lucky. I  had a few sets of older rings and found a nice pair/match. But I get what you two are saying. That being that, for the purpose of reticle VS barrel alignment it won't matter a bit.  Plus who knows if the rail is even parallel to the muzzle exit line anyways...just "un-cant" the gun to plumb when you shoot (simply genius BTW, my favorite kind) ....  So I do get it.

But all things being equal...and assuming good tolerances on a gun's manufacture, why not try to keep the reticle optically centered as well?  Avoiding offset in the rings that MIGHT be avoided, if you can do it, could keep you optically centered better. That is rather than trying to correct with excessive scope windage adjustment that MIGHT be avoidable.

I may even revisit some existing set ups to see if deliberately reversing one mount to the other side can improve my optic centering. They are all getting a vertical reset this way now anyways...

But it may be wise to point out what you did so people don't assume it will always work.

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Offline Relentless Holiday

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delete of a repete
« Reply #65 on: January 22, 2018, 12:44:41 PM »
delete of a repete
« Last Edit: January 23, 2018, 03:28:01 PM by P. O. I. »
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Offline nervoustrigger

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Re: Cant errors
« Reply #66 on: January 22, 2018, 05:10:34 PM »
I agree that keeping the scope near its center is useful.  There is no use centering it if you mount it on the rifle and then have to crank the turrets nearly to the limits to get it zeroed.
 
But please understand a scope that’s offset to the left or right has absolutely no negative effect on this goal whatsoever.  To clear this up, it sounds like we need to define what is meant by “offset”.  When I say offset, I mean the sort of thing introduced by using an 11mm mount on a 3/8” rail.  This error is completely erased by simply rotating the scope so its vertical crosshair intersects the bore.
 
It’s not the same thing as flipping the front ring and rear ring opposite of each other (re: the scenario where the screws are on opposite sides).  That is indeed likely to point the scope in a divergent direction from the bore.  In general, that’s a big no-no unless you have some other source of error (e.g. bent barrel) that it just happens to help counteract.  Also, I should mention you can buy mounts that are self-centering but frankly they are a solution to a non-problem when you know how to align the scope to the bore as previously described.
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Offline rsterne

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Re: Cant errors
« Reply #67 on: January 22, 2018, 08:40:29 PM »
Additionally, if the vertical crosshair intersects the bore with the scope optically centered.... and you hold the crosshairs level when shooting.... the only time you will have to dial in windage is if the dovetails are not parallel to the bore.... or if the rings are off center (like might happen if you reverse one ring).... The most common error made in mounting scopes is trying to correct offcenter mounting by cranking in windage.... instead of rotating the scope in the rings (while the scope is still optically centered) until the crosshair intersects the bore.... and then canting the rifle if necessary to get the crosshairs level when shooting....

I had several scopes where the windage was cranked over a long ways.... every one of them returned almost to center by first optically centering the scope, and then rotating it in the rings until the vertical crosshair intersected the bore.... Only slight windage adjustment was then necessary to fine tune the zero....

Bob
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Offline Relentless Holiday

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Re: Cant errors
« Reply #68 on: January 23, 2018, 03:32:27 PM »
Agree and agree. 8)
« Last Edit: January 23, 2018, 03:34:50 PM by P. O. I. »
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Offline Relentless Holiday

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Re: Cant errors
« Reply #69 on: October 18, 2018, 11:57:58 AM »
BACK UP TOP WITH THIS AGAIN.

It's come up elsewhere once more.
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Offline Csexton

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Re: Cant errors
« Reply #70 on: December 01, 2018, 01:55:46 PM »
Great post.
I feel that my Bubble Level forces me to keep the cant of my gun in the same position for each shot.
My groups are much tighter at 50 plus yards with it.
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Offline Relentless Holiday

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Re: Cant errors
« Reply #71 on: April 08, 2019, 09:41:50 PM »
BTT.

This deseves a sticky.
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Offline CaptVideo

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Re: Cant errors
« Reply #72 on: April 08, 2019, 11:04:48 PM »
Glad this popped up. Great post!
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Offline jfhall27

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Re: Cant errors
« Reply #73 on: April 21, 2019, 05:55:37 PM »
Additionally, if the vertical crosshair intersects the bore with the scope optically centered.... and you hold the crosshairs level when shooting.... the only time you will have to dial in windage is if the dovetails are not parallel to the bore.... or if the rings are off center (like might happen if you reverse one ring).... The most common error made in mounting scopes is trying to correct offcenter mounting by cranking in windage.... instead of rotating the scope in the rings (while the scope is still optically centered) until the crosshair intersects the bore.... and then canting the rifle if necessary to get the crosshairs level when shooting....

I had several scopes where the windage was cranked over a long ways.... every one of them returned almost to center by first optically centering the scope, and then rotating it in the rings until the vertical crosshair intersected the bore.... Only slight windage adjustment was then necessary to fine tune the zero....

Bob

This thread is great and being new to this, I've learned a lot. 

Regarding this post from Bob, is the technique of aligning the vertical crosshair of the scope with the bore only effective with a scope that is optically centered or does this still work if the windage turret has already been adjusted?  I know I currently have a can't issue (shooting to one side closer than my zero and the other farther than my zero) but do I NEED to reset my scope's optical center before aligning?  I understand there are benefits to this but is it absolutely required to have it optically centered for this to work?

Thanks!
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Offline rsterne

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Re: Cant errors
« Reply #74 on: April 21, 2019, 07:20:52 PM »
I would optically center the scope before aligning the crosshairs with the bore.... but you don't need to be anal about it.... Counting the clicks and setting the scope in the middle of its travel is good enough.... Then once you use the mirror and align the crosshair with the bore, you won't have to crank in a bunch of windage, and will remain close enough to the optical center of the scope....

Bob
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Offline jfhall27

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Re: Cant errors
« Reply #75 on: April 22, 2019, 01:12:17 PM »
Did a quick click count optical center.  Used the mirror trick to get things aligned, zero’d at 30y (windage was only off by a few clicks) and am now shooting on the vertical line from 10y to 50y.

Brilliant and super easy!  Thanks!
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Re: Cant errors
« Reply #76 on: August 26, 2019, 09:24:36 AM »
I would optically center the scope before aligning the crosshairs with the bore.... but you don't need to be anal about it.... Counting the clicks and setting the scope in the middle of its travel is good enough.... Then once you use the mirror and align the crosshair with the bore, you won't have to crank in a bunch of windage, and will remain close enough to the optical center of the scope....

Bob

How does the angle of the mirror effect the outcome. I use the mirror method myself; but I wonder how true my alignment is, if I'm not squared off with the mirror correctly.
Also... Have you found that it makes a difference if you align the crosshairs with the bore, versus aligning the crosshairs with the objective lens?
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Offline Bryan Heimann

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Re: Cant errors
« Reply #77 on: August 26, 2019, 10:46:03 AM »
That is why I miss.  It's not because I can't.  It cause my scope can't. 

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Re: Cant errors
« Reply #78 on: December 29, 2019, 04:57:18 AM »
This guy set up two identical scopes with quick release on a 6.5 Creedmoor.  One had the scope reticle aligned to the flat on the receiver.  The other had the vertical cross-hair aligned to a plumb line, despite the rifle being slightly canted to match the shooters comfortable hold:  youtube.com/watch?v=eCoHG23TQcY

The results may surprise you...
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Offline Scotchmo

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Re: Cant errors
« Reply #79 on: December 29, 2019, 04:53:26 PM »
This guy set up two identical scopes with quick release on a 6.5 Creedmoor.  One had the scope reticle aligned to the flat on the receiver.  The other had the vertical cross-hair aligned to a plumb line, despite the rifle being slightly canted to match the shooters comfortable hold:  youtube.com/watch?v=eCoHG23TQcY

The results may surprise you...

At 1000yrds - not surprising. As long as the reticle was held vertical (no gun-cant), the small amount of scope-cant needed to get the rifle comfortable will be insignificant.

With airguns, we often shoot as close as 10 yards. At 10 yards, scope cant issues will be 100x as much as it is at 1000 yards. It's a function of scope_height/distance_to_target. You would not likely see the error at 1000yards, but you would at 10 yards.

Also - if you are shooting at only one distance (whether it be 10yds or 1000yds), it does not matter at all, as long as you are sighted in (elevation and windage) for that one distance.
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