Measuring Base to Ogive Length w/ Hornady OAL Gauge

Discussion in 'Reloading' started by Catfur, May 29, 2013.

  1. Catfur

    Catfur Well-Known Member

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    I picked up a Hornady L&L OAL gauge, and am using it to measure the Base to Ogive length (actually COAL with the bullet loaded to the lands) in my 6mm Rem.

    I am getting wildly different lengths when I try to load the modified case short, and then tap the bullet out longer (which seems to be what the instructions recommend), but consistent lengths when I load the bullet long, and then use the rifling to stop movement of the bullet while moving the case forward. The lengths measure using the second method are also almost .15" longer.

    Does anybody have any advice or just thoughts?
     
  2. varmintH8R

    varmintH8R Well-Known Member

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    I run a cleaning rod down the muzzle, and use counter-pressure to gently "sandwich" the bullet back and forth into the rifling. I've done some blind tests and my results are pretty consistent.

    Good luck!
     

  3. el si

    el si Well-Known Member

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    Don't forget to measure the modified case headspace length and note the difference between that and your resized cases.
    Why not let your groups tell you what is the best seating depth? Touching the lands is just a starting point anyways. Go up and down in depth and see what shoots the best for your gun.
     
  4. Mikecr

    Mikecr Well-Known Member

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    The Hornady/Stoneypoint method is just poor in every regard.
    To begin, it assumes chamber dimensions and that a case used in measure would fit correctly(w/respect to what?).
    With this, many get poor/inconsistent measurements.

    I personally use an RP Tool, which is a cleaning rod with an end flat, and no case is used. It's just reference bullet tip with ogive against lands -to boltface. This is followed by seating THAT bullet in any case to reach that COAL, and then measuring with a comparator to get touching OgvOAL. It's just a point of reference.

    As el si implied, fear not about it.
    It's useful only in logging reference. That is, 'best results were found at':
    - 8thou off touching
    or
    - 2.693 OgvOAL
    Either provides the same function.
     
  5. Zep

    Zep Well-Known Member

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    Mikecr - I agree with your comments on the Stoney Point, I use a wood dowel against bullet tip and move back and as VarmintH8R states. Yes it is a reference but it takes a heck of a lot of practice to get something to work with. Can you give us some more info on the RP Tool?
     
  6. Mikecr

    Mikecr Well-Known Member

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  7. woods

    woods Well-Known Member

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    Best $25.00 I ever spent

    I still use the Hornady tool for holding the bullet to the lands but the RP tool for the actual measurement. Get very consistant readings

    But the trick with the Hornady tool is to use light pressure and the same everytime. I did not have much luck with toggling it back and forth at the lands. Seat the modified case firmly into the chamber and rotate a little to make sure it is all the way in the chamber, set the bullet deep in the modified case, release the lock stem on the gray rod and with one finger lightly but firmly with one motion push to the lands.

    You will have a difference because of headspace on non-belted modified cases

    For example on my 06, MODIFIED CASE datum measurement
    [​IMG]

    FIRED CASE datum measurement
    [​IMG]

    The good thing is that the modified case datum measurement difference will put you FURTHER from the lands than you think you are, which will keep you from seating into the lands and increasing pressure

    Not a big deal cause as someone has mentioned, it is all relative and as long as you do it the same, no problem

    It is nice to have 2 flat surfaces on the RP tool to take the final measurement

    [​IMG]
     
  8. Zep

    Zep Well-Known Member

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    Thanks woods.

    But I still don't have a grasp of the RP Tool. Would you please give us an explanation of how to use it again. Do you actually take one of the collets off the rod for the first measurement and then put it on for the second?
     
  9. woods

    woods Well-Known Member

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    Sure, but I like pics and it may take 2 posts since this site only lets you post 6 links in any one post

    The RP tool is a 30" long .187" diameter stainless rod, threaded at the end to take a .250" brass tip

    [​IMG]
    [​IMG]

    with 2 well made allen head collets

    [​IMG]

    The tip can be removed for any caliber below 257 but will won't work for 17 calibers

    First step is to insert the rod WITH COLLETS attached but out of the way down to the bolt face (make sure the firing pin is in the retracted position, don't ask me how I know) and lock the outermost collet

    [​IMG]

    NOTE that the innermost collet is already part of this dimension so it is "allowed" for in the final measurement

    Remove the bolt and insert bullet to the lands. This is the only step subject to variation as has been discussed. I use the Hornady tool but a dowel rod will work if you don't push on it too hard

    [​IMG]

    Insert the tool back down to the bullet tip and lock the innermost collet

    [​IMG]



    (continued)
     
  10. woods

    woods Well-Known Member

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    Measure BETWEEN the collets

    [​IMG]

    Now like Mike said, take that bullet out and keep it separate. You want to use that bullet when setting your seating die, set it for the OAL desired. IOW seat the bullet to the OAL (to the tip) where you want it (measurement minus jump) and then take a comparator measurement on it. That will allow you to use the comparator to check seating throughout the multiple load seating process and be checking close to the ogive and take the error induced by variations in bullet tips out of the process.

    The tool can be used for any caliber except the 17's and you will find other uses for it. It is the only way I have found to check headspace on BELTED cases. Like pin gauges very useful to have around
     
  11. Mikecr

    Mikecr Well-Known Member

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    Thank you Woods
    Awesome explanation
     
  12. Zep

    Zep Well-Known Member

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    Yes! - Thanks Woods!!
     
  13. Bart B

    Bart B Well-Known Member

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    Woods explanation is a good one for the tools used.

    I don't know what cartridge is the one used in this thread, but if it's one that headspaces on the shoulder, that's the control point for measuring where a given diameter on a seated bullet's ogive is. The case shoulder's hard against the chamber shoulder when its fired. The case head will be somewhere between almost zero to a few thousandths inch away from the bolt face depending on how much spread there is between the case head and shoulder across all the loaded rounds. A few thousandths is normal with full length sized cases.

    So, if one wants the seated bullet to be exactly the same distance off the lands on all rounds when fired, the bullet seater has to use the case shoulder, not the case head, as its reference.
     
  14. woods

    woods Well-Known Member

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    So you're saying that if you set your FL die to size the case body and push the shoulder back, lock it down and size your cases, that there will be a "few" thousandths (in normal conversation construed to be >.002" & <.006" or so) difference between the dimension between the case head and shoulder??!!

    Uhhhh in what press?