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weighing brass

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  #8  
Unread 08-15-2009, 10:09 PM
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Re: weighing brass

Quote:
Originally Posted by Mikecr View Post
This is an opportunity for you to find a reasonable interpretation.
Catalog and fireform the spread, then MEASURE their H20 capacity.
With that, you'll learn the significance of your brass weight variance.

Your capacity may follow.
Or, follows inconsistantly
Or, It might not correlate at all.

It's your brass
After a little testing the results are; the 206 brass holds 1.2 grains less powder (r17) than the 198-200 brass. also the 206 brass creates a flyer EVERY time when used with the lower weight brass. all the other weights of brass shoot very well. so everything over 205 goes in the melting pot.
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  #9  
Unread 08-16-2009, 09:30 AM
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Re: weighing brass

Weighing brass is a complete waste of time done by folks who want to "feel" better about their brass... Weight itself has nothing to do with the internal volume of the case, which is what you want to determine. Internal volume has everything to do with the pressure curve once the propellant is ignited and sends the projectile down the tube. The larger the variation of the internal volume of the case is proportional to the difference in pressure created and of course affects your POI. This is one of only to many to list variables that must be controlled to achieve the best and most consistent accuracy from any given combination of components, processes and procedures.
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  #10  
Unread 08-16-2009, 12:06 PM
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Re: weighing brass

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Originally Posted by Boss Hoss View Post
Weighing brass is a complete waste of time done by folks who want to "feel" better about their brass... Weight itself has nothing to do with the internal volume of the case, which is what you want to determine. Internal volume has everything to do with the pressure curve once the propellant is ignited and sends the projectile down the tube. The larger the variation of the internal volume of the case is proportional to the difference in pressure created and of course affects your POI. This is one of only to many to list variables that must be controlled to achieve the best and most consistent accuracy from any given combination of components, processes and procedures.
While that may be true sometimes in this case the weight of the brass had everything to do with the internal case capacity. all of the 206 weight brass had considerably less internal volume than even the 204 weight brass. all of the brass in the bag preforms well except the 206 stuff.
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  #11  
Unread 08-16-2009, 02:03 PM
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Re: weighing brass

Glad you found a correlation for your brass bud.
See, we really couldn't have guessed about what's what with YOUR brass.

Also keep in mind that you'll need to validate this correlation with each future lot. So log your findings because it may be tough to remember down the road.

Good job
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  #12  
Unread 08-16-2009, 02:10 PM
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Re: weighing brass

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Originally Posted by Bud Martin View Post
While that may be true sometimes in this case the weight of the brass had everything to do with the internal case capacity. all of the 206 weight brass had considerably less internal volume than even the 204 weight brass. all of the brass in the bag preforms well except the 206 stuff.

Bud,

What you have found is exactly what I have found. When dealing with a single lot of brass (where you would expect the alloy to be consistent), I don't understand why weight wouldn't correlate to internal capacity?? With internal capacity being so important to a loads performance, I don't understand why more people don't do a quick segretation of their new brass like you have done.

AJ
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  #13  
Unread 08-16-2009, 05:11 PM
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Re: weighing brass

"I don't understand why weight wouldn't correlate to internal capacity?? With internal capacity being so important to a loads performance, I don't understand why more people don't do a quick segretation of their new brass like you have done"


I'll answer that; People are lazy..
They reason that everything is clean, simple, and easy.
They want brass weight to resolve things because it's way easier than measuring capacity. Shooters go to great lengths to reason away neck turning just the same.
Or to endure torturous cold barrel load development? No way
Way easier to shoot hot groups and assume all other conditions hold.

Anyway, brass is alot heavier than water or powder. I know it's easy, but you can't just generalize that brass weight variance directly correlates with actual case capacity. Especially without knowing where the weight is. It could be primer pocket + rim - groove..
Capacity has to 1st be measured and verified, as was the case here.

The truth is never known without challenging it from all directions.
This,, because only the truth passes all tests.
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  #14  
Unread 08-16-2009, 06:20 PM
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Re: weighing brass

Quote:
Originally Posted by Mikecr View Post
s and assume all other conditions hold.

Anyway, brass is alot heavier than water or powder. I know it's easy, but you can't just generalize that brass weight variance directly correlates with actual case capacity. Especially without knowing where the weight is. It could be primer pocket + rim - groove..
Capacity has to 1st be measured and verified, as was the case here.
...

Mikecr,

I've never weighed cases from the same lot that didn't have a 100% correlation between weight and capacity. If the outside dimensions are the same, then the amount of brass would correlate directly to the internal capacity. I've never noticed a large variance in rim/groove thickness within a given lot. I always prep the primer pockets and debur the flash holes. If it's a chambering that will allow me to shoot the brass first (not a barrel burner), I'll shoot, prep, trim and then segregate.

All the volume measurements I've done have correlated quite well to the weight of brass that was once fired and then prepped. (all the same lot).

On the other hand, I've had rifles/loads that didn't notice the difference.

AJ
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