Case Volume / Pressure / Charge Weights?

[Mike_Honcho]

I have been using Winchester cases for .300WM but recently came across an opportunity to purchase a bunch of Black Hills cases - all the same year. I have read all the speculation about who makes the cases for Black Hills and decided I need to test the case volume.

I filled several Win and Black Hills cases absolutely full of TAC (very fine ball powder) and then weighed the amount of powder. There is a 2% volume difference in favor of the BH cases.

So here is my question - let’s just say my old load is 72.0 grains of whatever in the Winchester cases. Does that sort of roughly translate into 73.4 grains of whatever with the Black Hills cases in order to create = pressure / = speed of projectile?

 

[spife7980]

No. It’s not a linear relationship

New brass, new load.

 

[918v]

How much do BH weigh?

 

[Huskydriver]

I always start a new batch of load development when I change a major component of a load.

 

[Mike_Honcho]

Volume was @ 99 grains (Win) vs 101 (BH)

 

[47guy]

weigh the cases with H2o if you want a closer idea of internal capacity....and be careful like spife said new brand new load...i blew the heads off cases in a 300wm using the same load in a different brand of brass when i first started loading.

 

[JMGlasgow]

Years ago I read an article about Black Hills, and in the article the owner of Black Hills said his brass is made by Winchester.

 

[918v]

Volume was @ 99 grains (Win) vs 101 (BH)

But how much do the cases weigh?

 

[Mike_Honcho]

But how much do the cases weigh?

Why would I care? Thickness of brass.... it’s the internal volume.... am I missing something?

 

[Mike_Honcho]

Years ago I read an article about Black Hills, and in the article the owner of Black Hills said his brass is made by Winchester.

I have too. Both seem to be pretty consistent @ 2% margin in volume. Not sure I believe that rumor.

 

[918v]

Why would I care? Thickness of brass.... it’s the internal volume.... am I missing something?

You established your stated case volume incorrectly by pouring powder into a case that wasn’t fired in your chamber. The correct way to establish case volume is to fireform both cases, then measure case volume. Absent that, case weight is the only indicator. I know that Win cases weigh between 233-242grains. If your BH cases weigh 250 like FC, then they will have less case volume than Win.

 

[Mike_Honcho]

No...

I took my cases and sized them per my dies....then took the BH cases annealed them and sized them through my dies. So aren’t they the same?

 

[918v]

If they sized the same and trimmed to the same length, then yes, but you should use water and not powder.

So you won’t tell me the weight because...

 

[Mike_Honcho]

Why is weighing the case important?

Why is water better? I am dealing with meniscus and surface tension (not all the water drains / drain equally)

ETA - no calibrated dropper

 

[spife7980]

Weighing empty still gives you some indication. Just like your weighing with powder only it doesnt have the discrepancies of the powder.

Water doesnt have voids in it. I agree that ball powder is better than 4831 long cut but its also still a long ways from actually filling. Vibrate a case with it and youll see you can get a bit more in afterwards. Even the different rates that you pour it can effect how it falls and stacks inside the case.

Water fills all of the voids. Just make sure you fill it up the same each time. Using alcohol is another alternative that dries up much quicker.

One of these makes it easy and get rid of the primer variation.
http://www.xxicsi.com/primer-pocket-plugs.html

 

[Mike_Honcho]

Thank you both. I’ll weigh them and figure out a calibrated dropper....


I’ll update this with the BH / Winchester .300WM cases, as well as Lapua / Winchester / LC cases for .308 that were small based and trimmed - as I could never find such info on my own.

My initial goal is to work up the cases in parallel and watch the speeds (but after reading about SD and Chronographs I realize that readings my old cheap chrono may not mean much / be anywhere near as accurate as a much better chrono).


ETA:

.300 Winmag cases

Winchester averaged 243.7 grains / volume 5.8 ml

Black Hills (BLH 13) cases averaged 220.5 grains / volume 6 ml ~ @ 10% less weight 3% more volume

 

[918v]

Why is weighing the case important?

Why is water better? I am dealing with meniscus and surface tension (not all the water drains / drain equally)

ETA - no calibrated dropper

Brass weight is important because if all other dimensions are the same, the heavier case will have thicker walls and therefore less capacity.

When comparing cases, it’s best to use a flat meniscus.

Water is better than powder because it is more uniform no matter how you cut it. People add a little alcohol to minimize the surface tension issue. But even with meniscus/surface tension issues, you will see a pronounced difference in capacity between a 235 and a 250gr case.