Case Head Expansion
 

Anybody still measure case head expansion as a way of seeing pressures?

I have came to the conclusion that its not worth it. I think the only way it can be done is to measure a "new" case before and after firing and seeing the change.

I use a set of starrett mics.

I did a test this weekend, where I was building up a load for my STW. I took the load up in 0.5increments until I felt heavy bolt lift. The cases were new winchester cases. For the most part, I seen 0.0005" case head expansion with the "heavy bolt lift" cases. With the others, for the most part, I seen only 0.0003" or less. So I feel the theory is sound. But several cases did not coorelate the mic measurements and pressure signs.

It's probably a legitimate method. I don't use it because I only have a digital caliper that isn't precise enough to measure ten thousandths accurately. I look for the typical early pressure signs, harder than normal bolt lift and flattened primers. If I see either, I'll back down to the most accurate load below that that didn't show pressure signs.

Mike

I have a set of starrett anvil mics. Plus blade mitotoyos calibers. I don't really trust the calibers down to .0001. So only place to measure with the starretts is the rim itself. Or the belt.

Here's my thing. I bet it depends alot on brass brand too. In other words, if you had a pressure strain gauge. And lets say for both pieces of brass, you are reaching 70KPSI. But the webbing of brass A is stiffer. Brass B might show greater than .0005" expansion.

Just thinking outloud.

Ken Waters sure did like that method BC. What little I have reloaded I have measured it a little too. My calipers really arent good enough to do it seriously.

Thats what I was kinda thinking. Just heading into "shooting" season and was playing around a bit. 58th load? Thats just crazy. Surprised he didn't get a cracked neck at least. But his thoat is probably so tight it probably doesn't work it at all.

That sucks. I bought a bunch of this brass in .308 and .30-06. Oh well. You're not the only one I've heard this from. There are at least two others that have told me Nosler Custom brass isn't all that great.

Tom