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Thread: Measuring fired cases

  1. #1

    Measuring fired cases

    I was getting ready to do some reloading for the .270 and for no apparent good reason I decided to measure the 'headspace' of some fired brass. I use a Hornady tool and a Mitsy Vernier. My fired cases measure between 2.041 and 2.043 (de capped with a de capping die) so a 2 thou difference in fired cases. So my question, what variance do you guys get on fired cases and also your resized brass? Brand new Norma brass has a 2 thou variance as well. If I measure the same cases over and over I get the same result so I know its not my measuring.
    My resized cases have 1.5 thou variance.

    How does this compare with what you get?

    Ezzy

  2. #2
    I shoot .25-06 & have a variation of .0015". I measure using the Hornady HS tool & vernier, also I use the RCBS precision mic. tool. The dimension differences are similar with both tools.

    My fired cases measured de-capped (using a de-cap die) nominally average at 2.049". That's what I set also my F/L resizing die to resize. There can be slight variations in resizing, but I manage to keep down to +/- .0005"

    I think the difference in fired case dimension is simply down to how much 'springback' the brass each case has. As long as you take a fair selection of fired cases and pick a good mean average dimension to work to, all should be well. ATB

    N.B. According to the RCBS precision mic chart, the min HS dimension is: 2.0487" & max 2.0587". It's also the same for .25-06Rem. & .30-06Spr.

    Click image for larger version. 

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    RCBS PRECISION MIC CARTRIDGE HEADSPACE TOOL | Sinclair Intl
    Last edited by deeangeo; 18-03-2014 at 07:56.
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Zeiss 8x56, 110gn Nosler Accubond = Game Over!

  3. #3
    Where are you measuring from and to? Mind you, a .002 difference in almost any case measurement Isn't going to make any measurable difference to anything. If I were you I'd just stop taking that measurement
    You can't say muntjac without saying, Mmmmmm.

  4. #4
    Quote Originally Posted by Harry mac View Post
    Where are you measuring from and to? Mind you, a .002 difference in almost any case measurement Isn't going to make any measurable difference to anything. If I were you I'd just stop taking that measurement
    That's fine no problem with that...but a normal factory die set up instruction can generate .005" difference and thus your brass gets work hardened much faster. ATB
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Zeiss 8x56, 110gn Nosler Accubond = Game Over!

  5. #5
    Quote Originally Posted by Harry mac View Post
    Where are you measuring from and to? Mind you, a .002 difference in almost any case measurement Isn't going to make any measurable difference to anything. If I were you I'd just stop taking that measurement
    Seriously.~Muir

  6. #6
    If i set my sizing die as per factory instructions, I get very poor case life. 4 firings max before i start to see failures. The way i get around it is by setting my die to push the shoulder back as little as possible. Advice has always been to try to push the shoulder back by .001" for bolt actions and .002-.003 for semi autos. How can anyone consistently push the shoulder back by only .001" without risking making rounds that wont chamber? . By resizing to 2.038-2.040 i can get over 11 firings (and counting) from my brass.

    Thats why I wanted to see if i could reduce the variance.

    Ezzy

  7. #7
    Quote Originally Posted by ezzy6.5 View Post
    If i set my sizing die as per factory instructions, I get very poor case life. 4 firings max before i start to see failures. The way i get around it is by setting my die to push the shoulder back as little as possible. Advice has always been to try to push the shoulder back by .001" for bolt actions and .002-.003 for semi autos. How can anyone consistently push the shoulder back by only .001" without risking making rounds that wont chamber? . By resizing to 2.038-2.040 i can get over 11 firings (and counting) from my brass.

    Thats why I wanted to see if i could reduce the variance.

    Ezzy
    Ezzy.

    What you're doing looks spot on to me. It's highly unlikely that your measurements will match deeangeo's measurements. I too struggle to bump the shoulder back less than 2 thou.

    Best regards

    John

  8. #8
    Brass isnt going to expand on firing exactly the same everytime,3 to 4 fow on firing and about the same fl sizing, if they trim within a fow or 2 wouldnt be end of the world

  9. #9
    Cheers John, thats all I was after.

    Regards, Ezzy

    Quote Originally Posted by jcampbellsmith View Post
    Ezzy.

    What you're doing looks spot on to me. It's highly unlikely that your measurements will match deeangeo's measurements. I too struggle to bump the shoulder back less than 2 thou.

    Best regards

    John

  10. #10
    Quote Originally Posted by ezzy6.5 View Post
    If i set my sizing die as per factory instructions, I get very poor case life. 4 firings max before i start to see failures. The way i get around it is by setting my die to push the shoulder back as little as possible. Advice has always been to try to push the shoulder back by .001" for bolt actions and .002-.003 for semi autos. How can anyone consistently push the shoulder back by only .001" without risking making rounds that wont chamber? . By resizing to 2.038-2.040 i can get over 11 firings (and counting) from my brass. Thats why I wanted to see if i could reduce the variance. Ezzy
    Ezzy if it works for you that's fine & no reason to change. You can also just neck size cases until eventually you have to bump the shoulder back, doing so will certainly extend case life.

    Bumping the shoulder back to a close tolerance isn't necessarily difficult, but does require some 'technique' and patience. Depends how many rounds you load per session and what accuracy you're looking for from your brass preparation in addition to extending case life.

    For myself, I can take my time & tinker with my reloads, I only shoot a couple of hundred rounds a year these days.
    Care with brass prep pays dividends in more ways than one. ATB
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Zeiss 8x56, 110gn Nosler Accubond = Game Over!

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