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Stoney Point COL gauge - not so accurate?

 
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  #1  
Old 10-02-2006, 06:00 AM
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Join Date: Jun 2003
Location: Aussie in Italy
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Stoney Point COL gauge - not so accurate?

I noticed that I get different results from my Stoney Point Gauge and have always put it down to human error.

Recently I was trying to adapt a 7mm-08 case to fit and, predictable without tapping, it wasn't working well.

I tried using a fired case, putting a drop of superglue on the inside of the neck and slipping a bullet partially in then closing the bolt on it.

After 5 minutes I took out the cartridge and checked the COL. Just for curiosity I tried the same thing with a .308win round - having already checked and noted the COL the gauge gave me I found that there was a reasonable difference. The glued in bullets came out shorter, from memory by something like .1mm or so. I can and should check the exact discrepancy to post here, but has anyone else found the COL gauge in question to be a bit iffy?

I believe that the problem comes from the amount of force you can apply to the case in the chamber. With the Stoney Point gauge you cannot ram the case properly into the chamber. Closing the bolt on a round obviously sets it propery in the chamber and can give a more accurate reading.
True?
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  #2  
Old 10-02-2006, 08:13 AM
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Join Date: Nov 2005
Location: Texas
Posts: 226
Re: Stoney Point COL gauge - not so accurate?

Express, I know what you are talking about. I make my own cases for measurement. What I do is ream the neck slightly on my cases. The factory dummy cartridges they make, they thread and then stretch out the neck so the bullet will slide through This pushes against the chamber and I have caught the cartridge not completely in the chamber. This might be the issue you are dealing with. The next thing I would make sure you head space is set correct on your case.
The next thing is I always push hard on the tool when I get that measurement.I guess we should come up with something that will lock in like the bolt does.
I know the Stoney point is not the greatest tool but as long as you know what your working with and know it's weakness you can get buy ok.
Never the less your consern is valid in my book.

RH [img]/ubbthreads/images/graemlins/tongue.gif[/img]
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Old 10-02-2006, 08:21 AM
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Join Date: Oct 2004
Location: Atlanta, GA
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Re: Stoney Point COL gauge - not so accurate?

Express, I did an experiment using three people measuring the same inert loaded round on the same rifle in consecutive measurements. guess what- three differing lengths by as much as 0.003" as there are differing forces used to seat aginst the lands. Light, medium or hard engraving touchces. In addition, what are your results from checking actual bullet lengths? Did you uniform the lengths to one standard? Delta length = delta bc's= delta vertical impacts. If you can find layout blue, dark ink or soemthing to coat the bullets with you can read how wide or how long are the engraving marks then take the average length of say a 10 round sample. Overbore [img]/ubbthreads/images/graemlins/ooo.gif[/img]
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  #4  
Old 10-02-2006, 09:29 PM
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Join Date: Apr 2006
Posts: 47
Re: Stoney Point COL gauge - not so accurate?

If you want a true reading send Stoney point a once fired case. They will ream the neck and thread.

I don't use the Stoney point Gauge anymore. I take a once fired case and jam a bullet in then close the bolt. With the remaining neck tension in the once fired case this will usually yeald a bullet that is jammed approx .020. I use 00 steel wool to remove the marks left by the lands on the bullet and keep seating the bullet a few thou with my seater until I see no engraving from the lands. That is how I do it. [img]/ubbthreads/images/graemlins/wink.gif[/img]
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  #5  
Old 10-03-2006, 08:16 AM
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Re: Stoney Point COL gauge - not so accurate?

does the sinclair tool work any better???
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  #6  
Old 10-04-2006, 10:15 PM
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Join Date: Nov 2004
Location: Shiro, TX
Posts: 102
Re: Stoney Point COL gauge - not so accurate?

There are two different ways to attach the bullet insert to your dial calipers. Make sure you have it set up correctly so that the case head to bullet ogive is a straightline. This may account for the differences in oal.

Lance
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