Case head expansion

[wboggs]

I have been measuring case head expansion at 0.20" from the base of the case on nonbelted cases. Is this the correct place to detect expansion?

 

[JEFFPPC]

It is where I measure.

 

[quest450]

I use this little tool for measuring .200 line

 

[nmkid]

OK. I'll bite. Where did you get that?

 

[quest450]

Cartridge & Bullet Measuring Tools - .200 Line Tools - PMA Tool

www.pmatool.com

 

[Doug Beach]

.200 ahead of the base is generally about where the solid web ends, and may be .025” or so past the solid web. You aren’t really measuring case head expansion at that point. A blade micrometer in the extractor groove will measure expansion of the solid case head.

 

[LCazador]

To be more exact each time you measure, measure at the termination of the extractor slot before the .200" line.

 

[RegionRat]

At any rate, these dimensions and size changes make it worth a blade micrometer over a caliper in order to get better measurement. These dimensions are typically measured in the fourth decimal point in Inches, even though they may range into the third with change.
A caliper is better than nothing, but it should be mentioned that diameters are typically checked at the fourth decimal in a serious environment, while lengths might only be done to the third. Carry on.

 

[bozo699]

Cartridge & Bullet Measuring Tools - .200 Line Tools - PMA Tool

www.pmatool.com

Pat just makes nice stuff!…
Wayne

 

[Kracken McGraw]

Pat just makes nice stuff!…
Wayne

Good Gosh, now I need to spend more and get deeper on the Wabbit.

 

[bozo699]

Good Gosh, now I need to spend more and get deeper on the Wabbit.

I think you been at this long enough you can measure the .200 line without a set of these, I know I can but new tools are always cool and Pat makes nice stuff.
Wayne

 

[DeerHunter82]

Well, looks like I’m buying another gadget……

 

[quest450]

The handloader with the most toys wins

 

[bozo699]

The handloader with the most toys wins

I should be in the Hall of Fame then…….
Wayne

 

[quest450]

Lol, I'm getting there

 

[mikecr]

I have been measuring case head expansion at 0.20" from the base of the case on nonbelted cases. Is this the correct place to detect expansion?

Not really. You need to measure the widest portion of the fired case. The webline, wherever that ends up.
It doesn't take a mic, blade mic, or jig for this. Just slide calipers down to the widest datum (often visible), for a useful measure of the area last grabbing your chamber.

 

[Old Navy]

Looks like that chamber is too big.

 

[Doug Beach]

A lot of these suggestions don’t seem to have anything to do with the case head. We must be using different terminology.

 

[Alex Wheeler]

If your measuring the solid web for pressure signs, you want to measure behind the expansion point on the case. Pick a spot and mark it. Measure before and after firing. Most guys would say .0003 is max but I personally dont do it this way so I dont have a lot of advice.

 

[bozo699]

I have been measuring case head expansion at 0.20" from the base of the case on nonbelted cases. Is this the correct place to detect expansion?

Bill,
It doesn’t matter if it’s a belted magnum, rimmed non rimmed or rebated you measure directly in front or forward of the extractor grove. Say it was a belted magnum case it’s the area between the extractor grove and the base of the belt, I don’t have a case or a mic in front of me but it’s maybe a 32nd of a inch you have to measure on. The true way of measuring it would be a blade mic or one with small balls on your anvils it needs to read 4 decimals as .0005 is max!!!… you have reached max pressure for that case!.. you can’t take pressure reading on a Winchester case then switch to Remington as all manufacturers have different hardnesses. A caliper really isn’t the right tool and neither is a flat mic, but if that’s all you have then take a fine file and file a flat spot in your case then 180 degrees file another, you don’t need to take much, maybe .001 just a couple strokes or so. Get a base measurement off that case, load and fire and measure, continue upping your powder and measuring….. when it hits .0005 your at pressure!… at .005 you would be extremely over pressure ejector marks would show and hard bolt lift, more than that it wouldn’t fit in your shell holder anymore.
Wayne