How to figure Bullet seating depth

Discussion in 'Reloading' started by Greg Duerr, Apr 7, 2013.

  1. Greg Duerr

    Greg Duerr Well-Known Member

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    How do you guys figure your bullet seating depth?

    What tool do you use ?

    I have the sinclair bullet seating tool and a stoney point....................What I did learn was that you need a good pair of Calipers, not like the ones I bought 20 years ago from Midway for $20 I get a different reading each time and it never goes back to 0
    So far everything appears to be easy but this...................I would bet that When testing for accuracy I have loaded rounds that might be .005 to .020 different.


    Greg
     
  2. Magnum76

    Magnum76 Active Member

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    This is going to sound rough but has worked for me...

    Size a case.

    Seat a bullet way long past specs, like .100"

    Record Cartridge Over All Length.

    Chamber the "dummy round".

    Measure the "dummy round" again, record length. (chambering should push the bullet into the case some.)

    Using the inside part of the calipers, measure the marks left by the rifling to the case mouth.

    The difference between Chambered COAL and the marks on the bullet from the rifling give you where the rifling starts.

    Subtract another (.020"?) whatever you want to seat the bullet from the lands.

    Hope that made sense.

    So to answer your question, my "tool" that I use is a "dummy round".

    Another tool to get for the calipers in the Ogive attachment. This lets you consistently measure COAL from the Ogive of the bullet. Instead of the tip of the bullet which is inconsistent.
     

  3. MudRunner2005

    MudRunner2005 Well-Known Member

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    I do the whole dummy round deal, too. I use an old cleaned and size case (no primer or powder).
     
  4. silvercreekguide

    silvercreekguide Well-Known Member

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  5. Magnum76

    Magnum76 Active Member

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    Nice I like that too.
     
  6. DRSmith

    DRSmith Member

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    That is the way I have always done it.
     
  7. Sully2

    Sully2 Well-Known Member

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    I blacken my bullet with dark blue or black Sharpie. And when I feel the bolt close I open and close the bolt 2-3 times VERY GENTLY....that way I get a good heavy mark where the rifeling ends
     
  8. SGHinds

    SGHinds New Member

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    Very useful information. Thanks all.
     
  9. Reimche13

    Reimche13 Member

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    I do something very similar to what the others have listed. I found that sometimes the bullet wants to "stick" in the lands when pushing into the case so I made a "dummy" case same as the others have described. Then I used a dremel tool to split the neck of the case on both sides, thus letting the bullet slide into the case a little easier without getting stuck in the lands. This also lets me slide it out and re-measure several times to get an average. I also now use a tool to measure the length to the ogive as another has suggested, instead of measuring overall length. This gives you the length to the lands, you then can back off from there.

    I always start a master list then for each rifle and bullet combo as to the LTL (length to lands) that I keep in my book for reloading.

    This works for me but always keep an open mind for something better.

    Theo
     
  10. Md reloader

    Md reloader Well-Known Member

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    The Hornady(formerly Stoney Point) Overall Case Length Gauge works for me.
     
  11. Aldon

    Aldon Well-Known Member

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    I found that the occasional flyer dissapeared when I load each round by checking Ogive contact to case base length after having determined with Hornady/Stoney point the length to the lands. I often put a dummy round together for future reference.

    Basically I back off the seating die a bit, seat the bullet, measure base to ogive and tweak the micrometer die to get the ogive to lands distance exact. Slow exacting process but I am not loading in the gross and its part of the process of tinkering I like.

    If the cone in the die that accepts the point of bullet is perfect fit for the bullet tip, this would likely be unnecessary as the measurements would be consistant.

    Many feel this is wholly unnecessary to begin with.

    Each to their own I suppose but while this level of tedious effort is not necessary for a lot of my rifles it has proven to make a difference with a couple. My -06AI is particularly sensitive.

    I doubt this porcess would be of any value if I was shooting jambed into lands but when I set up my load for my hunting riifle, I wanted to make sure I could unload a round without pulling bullet and spilling powder. However rare that might be, it is too often.
     
  12. boomtube

    boomtube Well-Known Member

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    "What I did learn was that you need a good pair of Calipers, not like the ones I bought 20 years ago from Midway for $20 I get a different reading each time ..."

    The Midway and other Chinese calipers are quite good, especially so for reloading needs, and the prices make it rational for everyone to have them. The skill/touch required to use calipers and micrometers accurately and consistantly isn't as simple as many seem to presume, especially so on a curved surface like a bullet ogive.

    "...and it never goes back ..."

    Inconsistant gage zero comes from dirty jaws. Close the jaws on a clean sheet of paper and draw the paper out to clean.
     
  13. cowboy

    cowboy Well-Known Member

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    Have your wife save them anti static tissues she puts in the dryer when she is done with them. Wipe your caliper jaws down.

    I also use these old anti static sheets cut up and throw into my brass tumbler. No more little static particles to deal with. If you dump your brass/media though a screen sieve just pick out the pieces of black carboned up tissue and put in garbage. Best anti static wipe down cloths I have found.
     
  14. Red hunter

    Red hunter Well-Known Member

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    I use a fired case. deprime it then thread the primer pocket with a tap. I believe it is a 5/16 x 36 thread. this will then thread on my Hornady OAL gauge.