case head expansion

[TackDriver284]

I was bored and decided to do some measuring, measured the case head above the belt on the virgin Norma 300 Win Mag brass and on the fired brass. Difference on fired brass grew .005" on the case head above the belt, so I full sized with the bushing and measured again and its .001" less than the measurement on the fired cases. Is this measurement reasonable?

 

[truck driver]

You want to have some real fun measure the belt on a piece of virgin brass and then measure a once fired across the belt.

 

[TackDriver284]

Measured 10 cases virgin and fired, .003" expansion. Is it ?

You want to have some real fun measure the belt on a piece of virgin brass and then measure a once fired across the belt.

 

[SJB358]

CHE expansion is really been proven to be fairly unreliable in predicting pressures. Use the same VELOCITY load in three different cases and id bet you get different readings from the different pieces of brass. To me and my knuckledragger ways I'll stick with book or QL speeds dialed in to my rifles along with a reliable chronograph. I've worked all of the other ways of observing primers, CHE, etc and the books and QL have made me much safer ammo than other practices. Just my opinion. It's worth what you paid :mrgreen:

 

[DrMike]

Scotty is right to urge a degree of caution on CHE. CHE has a measure of validity when beginning with once fired brass and comparing subsequent firings. First firing measured against virgin brass is totally unreliable.

 

[IdahoCTD]

The cases come grossly under size from the factory so .005" of expansion on the first firing isn't uncommon. They were probably .507-.508 and .512 to .513 after? I think reamer specs are usually .513 ahead of the belt so your numbers might even be a little smaller.

 

[jimbires]

it's hard to tell a lot from once fired brass , it's not vary stable , it shrinks a lot . you might want to fire this brass a couple times and only neck size until it starts to get tight in the rifle . your brass will eventually end up fully expanded , this just speeds up the process . now measure this brass at fully expanded then again after resizing , this is how much your die is sizing . the die has to make the brass smaller for easy feeding . the only way to get your brass perfectly resized , without fear of over working , for this rifle would be to send fired brass to a die maker .

I did watch casehead expansion for PSI signs for a few years , I gave up on doing this . what you are watching for is less than .0002 " (2 tenths) of expansion on the second fire . virgin brass expansion means nothing .

 

[TackDriver284]

Exactly where would you measure expansion on a 7 RM case?

I did watch casehead expansion for PSI signs for a few years , I gave up on doing this . what you are watching for is less than .0002 " (2 tenths) of expansion on the second fire . virgin brass expansion means nothing .

 

[jimbires]

Exactly where would you measure expansion on a 7 RM case?

I did watch casehead expansion for PSI signs for a few years , I gave up on doing this . what you are watching for is less than .0002 " (2 tenths) of expansion on the second fire . virgin brass expansion means nothing .

measure belted cases right on the belt . if you are shooting a nonbelted case , you would measure right above the extractor grove . right where the belt would be if it had one .

 

[TackDriver284]

I only have a FL die with the bushing and a regular FL sizing die, so that won't work? You mentioned to neck size. Thanks Jim.

Exactly where would you measure expansion on a 7 RM case?

I did watch casehead expansion for PSI signs for a few years , I gave up on doing this . what you are watching for is less than .0002 " (2 tenths) of expansion on the second fire . virgin brass expansion means nothing .

measure belted cases right on the belt . if you are shooting a nonbelted case , you would measure right above the extractor grove . right where the belt would be if it had one .

 

[jimbires]

yes you can kind of neck size with a FL die . just turn your die up about 1/2 turn . this will raise the die about .035" and at that you shouldn't size any of the brass, except part of the neck.



I found the info I have on watching pressure . it's in a reloading manual Lyman#48 , pages 96 -101 . measuring CHE is about three paragraphs on pages 99 and 100 . if you want to read this PM me your email address and I'll email this info to you . all six pages are worth reading . info on reading primers , CHE , case head condition , using a chrony


I can't figure out how to post this info from my scanner , so if anyone wants it I can email it to you . just PM me your email address . or maybe I can email it to one of you guys and you can post it up for everyone interested .

 

[TackDriver284]

Jim, PM sent.

 

[Darkhorse]

I have an old Nosler loading manual Number 2 and there is an article, Bob Hagel wrote it, that goes into detail on working up a max. hunting load for "Your" rifle. Measuring CHE and belt expansion were part of his process.
I have measured the belt expansion on several warm loads and found the process to be right on if done right.
First thing I do is buy a box of factory loads and pull the bullets to get the brass. I make a mark on the belt with a magic marker so I'm sure to mike at the same place each time. I put a number on each case and write down the belt measurement for each one. Then I load one each with progressively more powder and write that down also.
Each shot I measure the belt. When the "New" belted case shows .0015" expansion on the back of the belt back off 1 grain and you should have a safe maximum load in "That rifle".
I have only used this on belted magnums but with non belted cases all the instructions are different so don't use these figures with non belted cases.
To do this you must have a set of 0-1" micrometers that measure to a tenth of a thousandth's. You must know how to keep them calibrated and adjusted. And most of all you must know how to measure and read them.
I was in the manufacturing, tool & die trade for over 40 years and can tell you truthfully that most people who think they can measure and accurately read .0001 micrometers in reality cannot. Sorry if I hurt any feelings with that but fact is fact.
I trust my skill when working up "over the book" loads but I won't trust anybody else's even someone I know has the skill.