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seating depth problem

 
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  #8  
Old 04-12-2011, 01:49 PM
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Join Date: Mar 2011
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Re: seating depth problem

Quote:
Originally Posted by cookjp View Post
I am using the hornady comporator set to measure OAL off the bullet ogive, and it is not a compressed load.
Ok.. Is it possible that some of the primers are not seated to the bottom?
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  #9  
Old 04-12-2011, 07:25 PM
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Posts: 93
Re: seating depth problem

I believe youre right Buck Snort, I got to thinking the same thing and checked a few and sure enough not all the primers were seated flush. I have had these shells awhile and was trying to use them up and guess these were preped before I started uniforming primer pockets. Thanks for all the help guys.
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  #10  
Old 04-21-2012, 05:12 AM
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Join Date: Jul 2011
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Re: seating depth problem

Here is a solution to accurate seating depths consistently

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  #11  
Old 04-21-2012, 08:05 AM
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Re: seating depth problem

The video illustrates a real problem for seating and other bullet measurements(like bearing comparisons), which is ogive radius variance. You can address this by qualifying ogive radius on your bullets right up front, like he was doing, or with a Bob Green bullet comparator(made just for this).

Missing from the video was realities associated with nose datum affects to consistent measurements. We all want land contact point consistent, but this is not always the best datum for good measurements, as it is also not a best contact for seater stems.

The stem that caused 14thou of contact difference was poorly suited for those bullets, as this is beyond affects of ogive radius variance -that low on the noses. But still, it's refreshing to see someone investigate the problem like he did.
Smaller differences are common in-lot, larger lot to lot.

Be careful not to refer to an 'ogive' as though it is the land contact point(that's not what ogive means). To date there is no such point established as a standard, and it will always vary locally.
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  #12  
Old 04-21-2012, 08:09 AM
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Location: Mountians of SW NC, near Asheville
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Re: seating depth problem

CRNA: "How do you measure from one particular point on an ogive and get consistent readings? "

The various comparitors all have a bore size hole (or near) in them; groove size bullets enter and stop at the correct point on the ogive. Readings are taken from that ogive contact point to the head of the case. (A compensation/correction is made for the body length of the comparitor itself.)













NS
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  #13  
Old 04-21-2012, 11:00 AM
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Join Date: Jul 2011
Posts: 56
Re: seating depth problem

Quote:
The video illustrates a real problem for seating and other bullet measurements(like bearing comparisons), which is ogive radius variance. You can address this by qualifying ogive radius on your bullets right up front, like he was doing, or with a Bob Green bullet comparator(made just for this).

Missing from the video was realities associated with nose datum affects to consistent measurements. We all want land contact point consistent, but this is not always the best datum for good measurements, as it is also not a best contact for seater stems.

The stem that caused 14thou of contact difference was poorly suited for those bullets, as this is beyond affects of ogive radius variance -that low on the noses. But still, it's refreshing to see someone investigate the problem like he did.
Smaller differences are common in-lot, larger lot to lot.

Be careful not to refer to an 'ogive' as though it is the land contact point(that's not what ogive means). To date there is no such point established as a standard, and it will always vary locally.
The stem did not cause the 14thou difference. I selected that bullet to show the extreme example. The curvature of the bullet caused the 14thou difference. I can prove this bc I will get the same reading on a particular bullet 10 out of 10 times. The method shows the inconsistencies in the curvature of the bullets and NOT in the seating stem. The point is that when you buy a box of bergers most of them have a 1-3 thou tolerance in the curvature/ogive but then there are those few bullets that are way way out of tolerance that will seat drastically different than the rest. These bullets are your fliers and should be culled from the rest or collected to be seated and used as a group. when i have the chance i will prove this by doing a video at the range comparing groups of bullets that are consistently seated vs those that are way out of tolerance mixed in and seated using the same die setting as the rest of the batch. you will be shocked.
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  #14  
Old 04-21-2012, 04:36 PM
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Re: seating depth problem

Ok gunner. My contention is that in-lot ogives usually don't vary so much as the 14thou anomaly, and I agree this would be a flier.
I've also found that gizzies like your reamer cut insert work alright with secant ogives, but less so on tangents. In the case of tangents, your original insert would probably produce better results(depending on the leade angle and ogive radius).

For qualifying ogives, it's best to set mid point-ish datums for comparison, so that you are away from extremes(meplat & leade contact).
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