Where do you measure?

[CatskillCrawler]

I've been starting to measure my case heads for expansion. I don't feel I'm getting accurate or viable data. First off, my measurements seem to fluctuate slightly every time I measure the same piece of brass. Secondly, I'm not noticing any trendable expansion irregardless of the charge or number of firings that any piece of brass has been subjected to. I believe this to be a good thing but when I see other high-pressure signs, I'm thinking I should be getting corroborating data from this measurement.

I have a few ideas as to why I'm not seeing what I think I should be seeing but I'm not confident I even know what I'm looking for! :?

A few questions:

- when measuring tapered cases, I have been measuring right above the extraction groove. Is this the correct location?

- Do I a need a blade-type caliper? It seems that standard caliper jaws give me different measurements with the slightest variation in placement.

- Is a standard dial indicating caliper with .001" capability accurate enough?

- how much of a change in diameter signifies a warning sign?

- am I wasting my time and would be better off loading more ammo or trying to figuring out how this is cheaper than....well....nevermind.

Thanks for your insight in advance.

 

[Guest]

You can't measure casehead expansion with a dial caliper, unfortunately. What you're trying to measure is to the ten thousandth, which is .0001". You need a blade micrometer. Other than that, you're measuring the right place. Just that the tool you're using isn't sensitive enough.

If you mic the casehead, you don't want them to stretch over .0003". That's approximately 50kCUP. You also only want to measure once fired brass, being fired for the second time. New brass will stretch more because it's not "set" yet, and at some point around firing 2-4, the brass work hardens in the head and it won't expand as much. So once fired brass is the standard.

 

[DrMike]

You can't measure casehead expansion with a dial caliper, unfortunately. What you're trying to measure is to the ten thousandth, which is .0001". You need a blade micrometer.

+1

 

[CatskillCrawler]

Thank you!

I will now remove this topic from my OCD inspired reloading required list and use my time on something I can more easily benefit from.

 

[338winmag]

If I am thinking correctly what you are asking about, at least for belted magnum cases:

This is what I have found:
You can measure this with the knife edge of a caliper.
The area "just above" the belt for most all virgin belted magnums measures at approximately .5065. After each firing, this case area can slight increase. Once this area starts to exceed .512, one can start having difficulty case chambering or case ejection. According to some, once the case gets past the .513 -.515 measurement, it is believed the case is past its useful safe reloading life expectancy.

My real life experiences:
At one time I was getting about 3-4 case firings for my 338 Win Mag before I started to see and slightly experience this "belted magnum case bulge" issue. Soon after my useful case life expectancy deteriorated. I purchased the "Belted Magnum Collet Resizing Die" from Innovative Technologies for use with magnum caliber reloading. The tool brings the case diameter back to around .510. I am now at 7-8 reloads on my 338 Win Mag brass and I see no unsafe reloading life issues. I also have used this tool for 7mm Rem Mag and 300 Win Mag. It works great!

But Something Interesting:
I had mentioned this tool to Scotty at one time and he mentioned that he did not see this magnum case bulge issue with his rifles. According to the inventor, this "belted magnum case bulge issue" will be experienced by all belted magnum reloaders, regardless of how tight the chamber is. For all the belted magnum rifles I have reload, I always did see this issue until --> I started reloading for another 300 Win Mag custom rifle. Even after 4 case firings, I never once had to use the "Belted Magnum Collet Resizing Die"!! This is not to say that maybe down the road, the cases would start showing the case bulge but with all other belted magnum rifles, I saw the bulge after 2-3 case firings. One 7mm Rem Mag was after just 2 case firings.

I believe this tool pays for itself after 3 case reloads. I also do not follow the inventor's suggestion of FS the case and then use this tool. I neck size every case firing and on the 3rd round I anneal, neck size and shoulder bump using a Redding body size die along with using this tool.

Just my 1.5 cents worth.
338 Win Mag

 

[CatskillCrawler]

338WM - I have seen and read about that resizing tool for belted magnums and recommended it to a friend. I will pass this link to him. I don't own or reload for any belted cartridges though. In fact, I try to avoid them.

I have been a "by the book guy" as far as powder charges go. I have now found that there are a few cartridges, which I feel, that can be loaded safely beyond these figures. I have been using a chrony and visual indicators to determine case health and pressure estimates. I hoped that if I could accurately measure case expansion that I would have another tool in my chest.

Thanks for your response.

 

[jimbires]

the guys are right . use once fired brass . use a blade mic .and .0003 max . measuring to a tenth is tricky so I keep my expansion under half a thousandth . I also align one jaw of my mic with a obvious spot with the head stamp . lets say we're loading 7mm rem mag . I'll align my fixed mic jaw with the 7 . this way my mic is measuring across the same position of the case . Jim

 

[GSSP]

I've been starting to measure my case heads for expansion. I don't feel I'm getting accurate or viable data. First off, my measurements seem to fluctuate slightly every time I measure the same piece of brass. Secondly, I'm not noticing any trendable expansion irregardless of the charge or number of firings that any piece of brass has been subjected to. I believe this to be a good thing but when I see other high-pressure signs, I'm thinking I should be getting corroborating data from this measurement.

I have a few ideas as to why I'm not seeing what I think I should be seeing but I'm not confident I even know what I'm looking for! :?

A few questions:

- when measuring tapered cases, I have been measuring right above the extraction groove. Is this the correct location? Where you measure depends upon the tool you are using. The best tool is a 1" blade micrometer that measures to .0001". With that tool you can measure above the extractor groove, in the groove or the rim itself. If you have a standard 1" .0001" micrometer with flat anvil faces then you can either measure the rim or just above the extractor groove. If you desire to measure above the extractor groove, you need to be sure the rim's diameter does not interfear. I've seen cases where the rim's diameter is greater than the area above the extractor groove and you can't get an accurate, repeatable measurement above the extractor groove.

- Do I a need a blade-type caliper? It seems that standard caliper jaws give me different measurements with the slightest variation in placement. Most, if not all, calipers will not measure to the necessary .0001" needed.

- Is a standard dial indicating caliper with .001" capability accurate enough? No

- how much of a change in diameter signifies a warning sign? Depends upon where you take the measurement. You'll see more change above the extractor groove than either the extractor or the rim. Above the extractor groove, I feel I've hit my absolute nose bleed max when I've hit .0007". Max in the other two areas is .0003", for me.

- am I wasting my time and would be better off loading more ammo or trying to figuring out how this is cheaper than....well....nevermind.I find when I'm entering territory where their is little to no data available, such as with my beloved 6.5x47 Lapua, measure case head expansion is invaluable. Also, when I feel that I'm just not seeing the velocities that the manuals tell me I should be seeing, low or high, I want the "RIFLE" to tell me what it likes, or "doesn't"

Thanks for your insight in advance.

 

[338winmag]

Hi Team,
I have seen a few times in this post where people are stating a "ten-thousandth" measurement. Please discern my "thousandth" numbers are for the diameter measurement just above the belt of a "magnum cartridge only".

This is what I have found:
You can measure this with the knife edge of a caliper. The area "just above" the belt for most all virgin belted magnums measures at approximately .5065. After each firing, this case area can slight increase. Once this area starts to exceed .512, one can start having difficulty case chambering or case ejection. According to some, once the case gets past the .513 -.515 measurement, it is believed the case is past its useful safe reloading life expectancy.

:mrgreen:
338winmag