Measuring case capacity

Reloading equipment, methods, load data, powder and projectile information.

Measuring case capacity

Post by Blr243 » 08 Feb 2019, 8:22 pm

I have been reading about trailboss powder and there is a mention sometimes about filling the case to 70 per cent capacity. So I filled a 303 case with powder to be about 10 mm short of the extreme top of case as I thought that’s where the base of my projectile would sit. And I thought of that as being max case capacity. Then as I started to think about those 13:5 grains of powder and how I need to calculate 70 per cent of it. Then I realised I’m probably doing this wrong. So when they talk about Case capacity, do they really mean filled all the way up to the top of the neck. And that’s how case capacity is measured ?
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Re: Measuring case capacity

Post by SCJ429 » 08 Feb 2019, 8:37 pm

You have it right, up to the base of the loaded projectile but no compressing the powder. Thirteen grains sounds about right, if you are worried try eleven and work up. Bladeracer will probably already have tried this and can give you more information.
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Re: Measuring case capacity

Post by Stix » 08 Feb 2019, 9:55 pm

Case capacity is measured to the base of the given projectile you're loading.
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Re: Measuring case capacity

Post by No1_49er » 08 Feb 2019, 10:51 pm

Go here for Hodgdon trail boss reduced load data: - https://www.google.com/url?sa=t&rct=j&q ... kqWrnoGv37
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Re: Measuring case capacity

Post by Blr243 » 09 Feb 2019, 6:26 am

Thank you very much !
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Re: Measuring case capacity

Post by bladeracer » 09 Feb 2019, 6:02 pm

Blr243 wrote:I have been reading about trailboss powder and there is a mention sometimes about filling the case to 70 per cent capacity. So I filled a 303 case with powder to be about 10 mm short of the extreme top of case as I thought that’s where the base of my projectile would sit. And I thought of that as being max case capacity. Then as I started to think about those 13:5 grains of powder and how I need to calculate 70 per cent of it. Then I realised I’m probably doing this wrong. So when they talk about Case capacity, do they really mean filled all the way up to the top of the neck. And that’s how case capacity is measured ?


Normally case capacity is measured for the full case using water, for TB they mean to the base of the bullet.
But I've never worried about it, I start by filling to around the bottom of the neck and then work up and down from there. I find there's rarely any velocity increase above that level though anyway.
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Re: Measuring case capacity

Post by SCJ429 » 09 Feb 2019, 7:37 pm

Funny you say that, I sometimes loose a bit of velocity when I push it.
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