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Scope Tracking

 
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  #8  
Old 10-28-2013, 05:07 PM
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Re: Scope Tracking

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Originally Posted by bruce_ventura View Post
^^^This!

Calibrating turrets using the "shooting the box" method seems like a waste of good ammunition too me. Getting good accuracy requires 3-5 shots per reticle position, which adds up to a box of ammunition.

Scott E's method is much more accurate and costs nothing. If you can set it up easily, then it's a much better method.

Having to hold the rifle in a vise and sight a calibration target is inconvenient for me, however. I prefer to use a Bushnell boresight collimator to calibrate turrets. That requires that the collimator be calibrated, which is an extra step, but I can do the entire process indoors using almost anything to hold the rifle.

Turret hysteresis or failure to track smoothly can also be diagnosed using the boresight collimator. Even failure to hold point of aim often can be debugged using a boresight collimator when the stock is the culprit.
good Info. I was going to mention the collimator but the one I have is an old one and I am not up on which ones are good today. Which do you use, the magnetic one and how is the etched glass setup?

Thanks,

Scot E.
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  #9  
Old 10-29-2013, 12:16 AM
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Re: Scope Tracking

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Originally Posted by Scot E View Post
good Info. I was going to mention the collimator but the one I have is an old one and I am not up on which ones are good today. Which do you use, the magnetic one and how is the etched glass setup?
I guess my favorite collimator is the Bushnell Professional Boresighter 74-3333. It provides three adjustable arbors that grab the bore when tightened. They are accurate to within about +/4 MOA, which is OK for most purposes. This model has an etched reticle with a 10x10 grid of 4 IPHY boxes, similar to many other models. The reticle pattern needs to be calibrated, usually by measuring the grid using a mildot reticle scope that you trust. They sure make reticle measurements easy, though. They have a dozen other uses as well.

This Bushnell model also has a removable cap on the back end that allows the instrument to be calibrated if it falls out of cal (usually because someone fiddled with it). Nearly the entire country is out of stock right now waiting for the Bushnell to make more. You can find used ones on eBay.

The magnetic collimators are not very accurate, but are needed for muzzle brakes. I made my own magnetic attachment that is as accurate as the muzzle brake it's attached to.

All the other models from Bushnell, BSA, Simmons, etc., provide caliber-specific spuds that are too small. They fit the bore loosely and are not repeatable.

Alley Supply sells the best bore spuds - very precise fitting - and they can be used with any collimator. The Alley Supply collimators are well made but they do not offer a grid pattern.

I've been developing a new collimator that I hope to put into production soon. I'm working on manufacturing issues right now. The prototypes have been working great.
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  #10  
Old 10-29-2013, 06:07 AM
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Re: Scope Tracking

I have also used the Bushnell/Cabelas grid collimators for quite some time. It works very well. In addition to testing turret movement, it can also be used to test vertical alignment(plumb) of the reticle through a 20-30 MOA elevation range, reticle aligment with the bore, attach the scope level, and insure everything is aligned. Good levels have to be used on the rifle rails and scope, and a secure rifle vice to do this. I will always do a tall target test at 100 yards when initially zeroing the rifle, to confirm actual click value, and plumb of the reticle. I have rarely, if ever had to realign the scope using this approach. I have found a couple of scopes over the years that had faulty tracking without firing a shot. You can also recheck scope tracking and alignment after a scope/rifle was subjected to a severe shock from a fall or other mishap.
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  #11  
Old 10-29-2013, 07:29 AM
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Re: Scope Tracking

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Originally Posted by bruce_ventura View Post
... the Bushnell Professional Boresighter 74-3333... has an etched reticle with a 10x10 grid of 4 IPHY boxes, similar to many other models.
Correction. It has a 20x20 grid of 4 IPHY boxes. There is a cross hair running through the middle of the grid. This a standard reticle pattern that most boresight collimators have.
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