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Gerting my scope aligned perfectly!

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Gerting my scope aligned perfectly!

Postby hungryrob » Sun Jun 14, 2009 10:05 pm

Is driving me mental!!!

I resorted to using the feeler gauge technique but because I have an after-market weaver rail on the gun, even that is giving me problems because when the pressure is equal on both sides, the ret is slightly off.

I've resorted to moving it by the thousandth of an inch and then shooting at 130 and 300 yards to test it... I seem to have fixed it at last tonight :roll:

I don't mind being out an inch or two but now that I have switched to the high mag Nightforce, I'm back shooting at 400 yards plus and the inch or two out at that range is significant.

Why isn't there a simple and absolutely perfect tool for this job :mad:
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Re: Gerting my scope aligned perfectly!

Postby hungryrob » Sun Jun 14, 2009 11:20 pm

Not convinced Kev, I've tried that before (wrecked a couple of old levels for the inserts) and like I said, it's OK for medium ranges but when dialling in out to 500 yards, the only way I have found to be successful is by shooting and even then the air has to be absolutely still.
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Re: Gerting my scope aligned perfectly!

Postby Beer Hunter » Sun Jun 14, 2009 11:31 pm

The bubble level works well for me - just remember the action must be levelled in both horizontal planes or you will be out.
Did you not try the technique I showed you at Denmill?
You can check by dialling in a 20 or 30 MOA lift at 100 yards. If its wrong then correct there.

Kev.
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Re: Gerting my scope aligned perfectly!

Postby Beer Hunter » Mon Jun 15, 2009 12:05 am

Beer Hunter wrote:...You can check by dialling in a 20 or 30 MOA lift at 100 yards. If its wrong then correct there...

Just thinking about that - its the perfect test......
You are going to need about 40 MOA of elevation for your 400 yard shots, so make a tall skinny target from 4 bits of A4 taped together and have a thick cross going through the centre and extending to the edges. Hang this up using a spirit level.
First zero in at 100 yards with your scope reticule leveled on the targets lines. Then dial in 20 MOA up and you should have a hole 20.944" up and dead on the vertical line. Now dial down 40 MOA and you should have a hole 20.944" down and dead on the vertical line.
If the scope is off, this will tell you immediately. It will also give you the true click values for the scope if you measure. Any error will obviously be magnified 4X at 400 yards.

If you also test at 25 and 200 yards, it will tell you if you have any crossover - I wouldn't be surprised as with the current setup you've got about 20 bits of metal between the bore and scope, each with their own tolerances.

You can pretty much forget about spindrift as it is only about 0.16" at 400 yards for your VG's.

Kev.
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Re: Gerting my scope aligned perfectly!

Postby Born Again » Mon Jun 15, 2009 12:32 am

The best way I could think of was to shine a laser along the bore and make sure that the vertical reticule element tracks on the laser dot from full up to full down. For a large centrefire rifle you could make a laser that fits into the chamber, for smaller rifles it's a bit more difficult.

This is a jig I made up to do the job on an air-rifle some years ago, the prism deflects the laser 90 degrees up the bore.

Image
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Re: Gerting my scope aligned perfectly!

Postby Beer Hunter » Mon Jun 15, 2009 12:43 am

That's an interesting idea, but how do you ensure that the very thin laser (at barrel distances) is fully alligned with the centre of the bore?

Even if it's only out by one 20th of a degree, that is still 3 MOA or 12.6" at Robbies 400 yards. Even then, that is only the error with zero cant or scope misalignment - with one or the other the error is magnified many times.

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Re: Gerting my scope aligned perfectly!

Postby Born Again » Mon Jun 15, 2009 7:46 am

Beer Hunter wrote:That's an interesting idea, but how do you ensure that the very thin laser (at barrel distances) is fully alligned with the centre of the bore?

Even if it's only out by one 20th of a degree, that is still 3 MOA or 12.6" at Robbies 400 yards. Even then, that is only the error with zero cant or scope misalignment - with one or the other the error is magnified many times.

Kev.


I found that if the laser wasn't pointing directly down the barrel, ie it was touching the sides, there was a distortion of the dot and crescent secondary laser dots. I could have made a plug for each end of the barrel with a small hole in but this was for a 0.177 air rifle and that degree of accuracy wasn't needed.
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Re: Gerting my scope aligned perfectly!

Postby The_Dogge » Fri Jun 19, 2009 11:47 am

Beer Hunter wrote:
Beer Hunter wrote:...You can check by dialling in a 20 or 30 MOA lift at 100 yards. If its wrong then correct there...

Just thinking about that - its the perfect test......
...
If you also test at 25 and 200 yards, it will tell you if you have any crossover - I wouldn't be surprised as with the current setup you've got about 20 bits of metal between the bore and scope, each with their own tolerances.

You can pretty much forget about spindrift as it is only about 0.16" at 400 yards for your VG's.

While you cant beat an actual firing test for verification, do you have any good tricks for actually making adjustments? Assuming this doesnt give you perfectly vertically aligned groups how do you adjust the scope with sufficient precision to correct it?
I can imagine expending quite a bit of ammunition on this before randomly getting it within tolerance!
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Re: Gerting my scope aligned perfectly!

Postby Beer Hunter » Fri Jun 19, 2009 2:14 pm

I set mine up using bubbles removed from levels. If you take your time, it comes out perfect.
Nothing beats testing it though - if your shots end up on the paper going 1 o'clock to 7 o'clock, then you need to turn your scope 30 degrees clockwise.

Kev.
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Re: Gerting my scope aligned perfectly!

Postby Born Again » Fri Jun 19, 2009 3:29 pm

The_Dogge wrote:
Beer Hunter wrote:
Beer Hunter wrote:...You can check by dialling in a 20 or 30 MOA lift at 100 yards. If its wrong then correct there...

Just thinking about that - its the perfect test......
...
If you also test at 25 and 200 yards, it will tell you if you have any crossover - I wouldn't be surprised as with the current setup you've got about 20 bits of metal between the bore and scope, each with their own tolerances.

You can pretty much forget about spindrift as it is only about 0.16" at 400 yards for your VG's.

While you cant beat an actual firing test for verification, do you have any good tricks for actually making adjustments? Assuming this doesnt give you perfectly vertically aligned groups how do you adjust the scope with sufficient precision to correct it?
I can imagine expending quite a bit of ammunition on this before randomly getting it within tolerance!


If you were to put an extra scope ring on your scope but with its base laying against the side of the action rather than on the rails and nipped up you could then loosen the main mount rings and use feeler gauged between the spare mount and the stock before re-tightening the main mounts - if that's clear. A simple bit of maths will convert the feeler gauge size to angle rotated.
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Re: Gerting my scope aligned perfectly!

Postby hungryrob » Fri Jun 19, 2009 3:46 pm

Born Again wrote:
The_Dogge wrote:
Beer Hunter wrote:
Beer Hunter wrote:...You can check by dialling in a 20 or 30 MOA lift at 100 yards. If its wrong then correct there...

Just thinking about that - its the perfect test......
...
If you also test at 25 and 200 yards, it will tell you if you have any crossover - I wouldn't be surprised as with the current setup you've got about 20 bits of metal between the bore and scope, each with their own tolerances.

You can pretty much forget about spindrift as it is only about 0.16" at 400 yards for your VG's.

While you cant beat an actual firing test for verification, do you have any good tricks for actually making adjustments? Assuming this doesnt give you perfectly vertically aligned groups how do you adjust the scope with sufficient precision to correct it?
I can imagine expending quite a bit of ammunition on this before randomly getting it within tolerance!


If you were to put an extra scope ring on your scope but with its base laying against the side of the action rather than on the rails and nipped up you could then loosen the main mount rings and use feeler gauged between the spare mount and the stock before re-tightening the main mounts - if that's clear. A simple bit of maths will convert the feeler gauge size to angle rotated.


That's it!!!!!!!!!!!!!!!!!!!!!

Brilliant

I do like the 'vertical line system' where you shoot (I use 75 yards) at a plumb line on a sheet of A3 size paper and dial up and down to check the alignment but I always found that adjusting it with feeler guages between the bottom of the scope and the receiver was to fiddly and even a couple of thou could set it off the other way...

This has to be the absolutely perfect system for alignment coupled with the plumb line mark and dialing up or down.....

Will be trying it tomorrow or Sunday and reporting back :thup:
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Re: Gerting my scope aligned perfectly!

Postby humperdingle » Fri Jun 19, 2009 5:57 pm

Crikey, what a stickler for accuracy! Goin for t'lympics this year, Rob?

I made do with 150 yards the other day. First real longish range testing of the .22-250. Zeroed first at 80 yards and then took a couple of shots at the 150 yard target. To my amazement, one shot was RIGHT in the middle of the bull, and the other a half inch to the right.

Not easy to see the target with my 8 X scope at that distance mind you!

Chuffed.
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Re: Gerting my scope aligned perfectly!

Postby Beer Hunter » Fri Jun 19, 2009 6:39 pm

Robbie,

I have a confession - I've been leading you on and I very much doubt you are suffering from excessive cant.

Lets take an extreme example where your scope is out by 5 degrees (even you would notice that, see the cross-hairs below) :
Image

In this calculation:
  • The smallest target squares are 1"
  • The scope cant is 5 degrees
  • the round used is .224" 36 grain VG's fired at 4100 fps
  • the red dotted line tracks the actual impact point from 100 to 400 yards
As you can see, even with this huge cant, at 400 yards you would only be hitting about 1.2" to the right.
Even with a totally implausible 10 degree cant, you would only be 2.3" out at 400 yards.

This leaves a few possibilities:
  1. the shooter is crap
  2. the calibre is crap
  3. the scope is crap
  4. the barrel is burned out
  5. the bullets have all the BC of confetti
  6. all of the above
I'll leave you to choose :razz: :grin:

Kev.
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Re: Gerting my scope aligned perfectly!

Postby varminter » Fri Jun 19, 2009 8:35 pm

I am continuously impressed by the amount of expertise on this forum. Thanks for all these ideas about scope mounting: I've always managed pretty much OK by the seat of my pants and a careful approach, but especially since I am grappling with a ring/scope disparity at present and fitting shims etc, I need all the help I can get. I too use small bubble-levels, but these don't give precision matches between scope and bases/receiver, just a good close guide. I might try that clever extra-ring/feeler gauge idea - though when Born Again writes, "A simple bit of maths will convert the feeler gauge size to angle rotated," I have to express my doubts and emphasise that I only just scraped O-level Maths...
Regards, Malcolm
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