Case head expansion measuring

[cdn moose]

Gentlemen, I was wondering if you wanted to measure case head expansion, would you have to use a blade type micrometer or can you you use a regular type anvil? I can see how you maybe wouldn't want to use a dial caliper, although the results do seem be repeatable just not reading low enough. Any and all opinions are appreciated.

Moosey

 

[Suputin]

Why would you bother?

When the case won't fit into the case holder of the primers drop out then the case head has expanded too much and the case should be chucked.

 

[cdn moose]

I thought maybe I might be able to learn something to add to my personal enjoyment of the hobby thats all,

moosey

 

[zuke]

I use a 0-1 Mic with regular anvil's that read's in 10,000's. I like to fire 4-5-6 factory rds and measure the case head in 3 place's to get a baseline number. When I put together my reload's I measure them to see how close I'm getting to the baseline measurement.
I have several dial caliper's but don't feel they read to a fine enough detail.

 

[cdn moose]

Thanks for the reply Zuke, do you mean you measure like 120 degrees apart around the case head or three seperate spots?

Moosey

 

[zuke]

I like to do it 120deg apart

 

[bigedp51]

Brass hardness varies by manufacturer so even base expansion of .0005 can be a sign of high pressure. So remember reading base expansion is like reading primers, it depends how hard the brass is. The most common method is with with blade vernier calipers or a blade type micrometer.

When are Pressures Too High?
http://shootersnotes.com/articles/when-are-pressures-too-high/

Lapua brass is the hardest of the commercially made brass and military cases would be harder. Below some competitive shooters will load the case until the brass flows into the ejector and then back off one or two grains. This lets the shooter know the elastic limits of the brass and how much pressure the case can take. A steady diet of reloads like this will enlarge the primer pockets "BUT" each rifle and the components will be different.

Below from Quickload, my practice AR15 ammo is only loaded to 50,000 psi and 5,000 psi below max chamber pressure. This makes sure cheap bastards like me get plenty of reloads out of my cases.