Shoulder bump and comparator readings

Discussion in 'Reloading Forum (All Calibers)' started by Alex Wheeler, May 14, 2019.

  1. jamesdmock

    jamesdmock Gold $$ Contributor

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    Hall of Fame shooter, Pat Byrne cautioned me when I first started shooting Benchrest to NOT trust feel. A feeling of tightness is often caused by the base not being sized properly and is not the length of the cartridge from base to shoulder.
     
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  2. tmwinds

    tmwinds Gold $$ Contributor

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    I agree, you can't determine shoulder bump by feel if the rest of the case doesn't fit. Shoulder bump is only one aspect of proper sizing.

    Where is fguffey? He could explain this where none would understand.
     
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  3. SPJ

    SPJ Silver $$ Contributor

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    He’s on the high road.
     
  4. Ledd Slinger

    Ledd Slinger Gold $$ Contributor

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    This is exactly where the importance of spending the extra money to have custom built sizing dies comes into play ;)
     
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  5. McGraw

    McGraw Silver $$ Contributor

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    Are you saying Guffey thinks he’s too good for us, Lol!
     
  6. Lone Hunter

    Lone Hunter Silver $$ Contributor

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    Yep, Because non of us can do what he does. He is the only one that can do anything right. The rest of us are dumbasses to him... The High Road.. Kinda Ironic don't you think..
     
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  7. nmkid

    nmkid Gold $$ Contributor

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    Man! I am a sucker for stuff like this! I was just getting ready to order some inserts for another tool. But, this looks like a new toy! Wouldn't have to look for inserts again.
     
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  8. Ccrider

    Ccrider Gold $$ Contributor

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    @nmkid there was one for sale on here a couple of weeks ago. Really neat tool and amazingly accurate and consistent.
     
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  9. Ledd Slinger

    Ledd Slinger Gold $$ Contributor

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    Yeah it's nice because it's very fast and simple to adjust for different cases. Can use it to measure bullet seating depth on larger calibers as well. Adjust the jaw so it makes contact at the start of the ogive right at the lands touch point.

    Only gripe is that the digital indicator doesn't have an auto shutoff and it takes weird little batteries. Sucks to replace them if you forget to turn it off cuz you have to do some searching to find them. Can get them on ebay or Amazon tho.

    Hard to set the jaw contact point back at the EXACT point point you had before when adjusting it for a different case, then going back to the same cartridge again, but consistency is what we look for and consistency, or perhaps lack thereof, is what it will show you.

    Cant see it in the photo I posted, but it actually measures in .0005" increments.
     
  10. SPJ

    SPJ Silver $$ Contributor

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    He still says the same things and gets similar reactions from THR members:cool:
     
  11. Uncle Ed

    Uncle Ed

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    The Lake City 5.56 case below is stamped 08 and for some reason the 9mm case will not touch its shoulder. :eek:

    [​IMG]

    And my Hornady cartridge case headspace gauge instructions tells you what adapter to use for specific calibers.

    RTFM :rolleyes:

    Below a Colt 5.56 Field gauge at 1.4736

    [​IMG]

    The field gauge in my adjusted Hornady gauge

    [​IMG]

    And a fired case from my AR15 reading very close to actual chamber headspace minus brass spring back.

    [​IMG]
     
    Last edited: May 15, 2019
  12. Ccrider

    Ccrider Gold $$ Contributor

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    Have you guys not learned, “let sleeping dogs lie.”:D
     
  13. newbieshooter

    newbieshooter :-) Silver $$ Contributor

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    Got this when I first started reloading several years ago. Figured one tool for all calibers/cartridges without having to deal with inserts and trying to measure with calipers .etc.... Quick and easy. Takes a few seconds to check cases after FL sizing to ensure each case shoulder is bumped .0015.
    Shoulder_bump.JPG

    From 2011:
    http://forum.accurateshooter.com/threads/larry-willis-headspace-tool.3757422/
     
    Last edited: May 15, 2019
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  14. L W P

    L W P

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    That's a nice tool, but does it measure at the .200" line. Just another spot to be sure of resizing F/L for a nice bolt close and lift.
     
  15. newbieshooter

    newbieshooter :-) Silver $$ Contributor

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    No. FL sizing dies are based on fired cases from each of my chambers. I also double check FL sized cases to ensure they chamber for a nice bolt close/lift.
     
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  16. Pwc

    Pwc

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    I use a home made comparitor for shoulder bump. It's not exact, but you can trim the pistol case to be square and flat. I colored Poor man's comparitor.jpg mine red so it won't be lost or mixed with other cases. Works for me.
     
  17. Rushty

    Rushty Silver $$ Contributor

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    Guess I got lucky with 3 relatively cheap Sinclair comparators..Left is BRA, centre is straight BR and right is 284, marked them up then ran comparator over them and to my surprise appears to be making virtually full contact at what looks like to be the same angles...I’ve never had any issues measuring bump but thought I’d check anyhow.
     

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