weighing cases...dry weight or wet weight?

C

coolcruiser

Guest
Today at the range a friend recommended to me that I weigh my 6.5 x 55 cases using water to fill the fired case instead of my current practice of simply segregating my cases after sizing by their dry weight. He said that he has seen a significant variation using water that did not show up in the dry weight of a case. Obviously we are talking about determining the true volume of a case. Any thoughts on this? Is it worth it to "wet weigh"?
 
Well since no one else has started the ball rolling.....

I think weighing cases any whichaway is about as effective in terms of accuracy as dancing naked, widdershins, around a road kill possum at the peak of the Vernal Equinox.

It is probably safer though, the weighing......

semis and pickups trucks y'know

be careful out there

on the turnpike

whewww

;)

al
 
Case weighing

I would think (dangerous I know) that if you wanted to know the difference in case capacity you'd have to weigh each case before and after you fill it. Brass is 8X heavier than water so the weight difference between cases is more likely going to be brass. The fill level can be a little bit arbitrary too. I will weigh a few cases, fill and re-weigh them to get an idea of average case capacity.

I work my brass (full length size, uniform primer pocket, deburr flash hole, neck turn, trim and clean) then weigh into .5 gr groups, which is less than .1 gr of water difference in case capacity. That is not the way others do it, just me. Having said that, since I now use Lapua brass and no-turn neck chambers I do nothing but check length and trim at maximum case length. I do weigh each powder charge. - nhk
 
coolcruiser said:
Today at the range a friend recommended to me that I weigh my 6.5 x 55 cases using water to fill the fired case instead of my current practice of simply segregating my cases after sizing by their dry weight.
Click to expand...

Welcome to the forums.
I have been shooting BR for a little short of 30 years at this point alongside many of the best and well known BR shooters around and I can honestly say this is the first time I ever even heard of weighing your cases filled with water. Most of us use cases like Lapua that as Alinwa stated are not really even worth weighing they are so consistant. If it makes you feel better do it the way he suggests but it sounds like a lot of wasted effort to me.
Dick
 
My recent findings

I too have heard people argue that case weight doesn't equal case capacity. So I did an experiment 2 weeks back with some once fired for forming, prepped 30BR Lapua Blue box brass cases I was sorting. After sorting by weight I took the 2 heaviest and 2 lightest cases and primed them. The heavy ones weighed 127.3g primed. The 2 lightest came in at 125.2g primed.

I then filled each of those 4 cases 3 times each with water and recorded the filled weight. The 2 lightest averaged 165.9g and 165.8g for their 3 loadings. The 2 heaviest cases averaged 167.4g and 167.6. The first loading on the dry cases always weighed .2g or .3g less then the subsequent 2 loadings. The weights were so constant and expected that I stopped after just 3 weighings each. From this I figure that you can roughly split the weight difference in half to get capacity difference in the BR case. As in 1g equals .5 percent capacity.

This was enough to satisfy me that case weight equals capacity close enough for my purposes and a full 1 percent case capacity from the 2g weight difference in a box is enough to keep me sorting brass by weight. I'm doing 8 other paper boxes of 6BR brass for 2 other loadings and the 2 lots I have have the same weight variation between light and heavy as the blue box stuff.

If you have Quick load, you can change the capacity by 1 percent and see for yourself what kind of velocity variation this kind of case capacity variation will cause and decide what case weight range is acceptable for your use.

Edit: I wouldn't sugest using blue box for a .330" 30BR neck unless you like .0025-.003" neck clearence on a cleaned neck.
 
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Jackie,
The Lapua blue box 6BR brass is thinner than the old cardboard box brass and the box I have can't be cleaned up any better than that. I have 2 pieces that didn't clean all the way around even at .003" clearence. If I'd have to guess I'd say the 1 blue box I have looks to be more uneven than the older stuff too.
 
What is the neck dia. of your chamber and neck dia. of your unturned brass before turning. Neck thickness before and after expanding to .30. Randy
 
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Hey Randy, if your question is directed to me, I did the whole box and have no unturned rounds left. Sorry but I have no record or rememberance of what it originally mesasured. Like I said above the brass was turned for a 330 chamber. Another thing on the thin blue box 6BR brass is that the neck seems to be far more uneven in thickness up at the top of the neck than the old cardboard box stuff which was more uniform the lenght of the neck. I've read somewhere that Lapua plans on going back to producing 6BR brass in the older demensions because of all the complaints. Not sure of that is true.
 
tricrown said:
...If you have Quick load, you can change the capacity by 1 percent and see for yourself what kind of velocity variation this kind of case capacity variation will cause and decide what case weight range is acceptable for your use.
Click to expand...

Have you validated the Quick Load software with a chronograph?
 
Nope

No Wilbur, I didn't. But I'd be interested in seeing if the 11fps or so difference can be verified by anyone with the time and desire to do so.
 
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