Case comparison

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MikieG7174

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I have federal cases that I have been using since 1997. Handing those over to my son and starting to use Blackhills Match cases.
You folks have any idea how Federal compares to Blackhills internal volume wise?
My 178 AMAX loaded with 44gr OF IMR 4064 is far from max. So my wonders are what kind of velocity shift I might have?
 

swampratt

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Seems like you have access to both of the cases.
Since different batch number of the case can change the volume you should test for yourself to get a good accurate measurement.

I like to use a ball powder like BL-C2 or aa#5 to fill a case to check volume.. I slowly trickle the ball powder into the case with a funnel .. then card it off and weigh it.

I usually take that same powder I just weighed and trickle it into another case of the same batch.. see if there is a difference in same batch cases.
 

Jcann

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I'm confused, are you wanting to compare the muzzle velocity of your reloads to store bought Blackhills 178gr loaded ammo? Or, you have once fired/new? Blackhills brass, but before you reload it, you want to know case volume as compared to Federal brass (to determine possible equality in muzzle velocity between the two).

I feel you're asking the impossible solely based on the H2O volume of the two cases. Bullet weight differences and bullet bearing surface differences can also add variances to your equation not to mention neck tension. Granted, these would probably be slight differences in velocity.

If I understand you correctly, you are wanting to know if both cases are loaded identical will they shoot within one another's ES/SD. The only way to know for sure is to run them through a chronograph.

BTW, The only way to get an accurate case volume measurement is with liquid. Think of putting marbles in a jar then fill it with water. If it holds water the marbles weren't a good media to measure volume. It's the same with ball powder, there will always be voids between the individual pieces of powder.
 
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