seating depth by oal guage or chamber method?

Discussion in 'Reloading' started by nelsonic, Jul 29, 2005.

  1. nelsonic

    nelsonic Member

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    I have an kimber 22-250 rifle that I used a oal guage on and measured the cartridge at 2.487 inches to the lands...upon chambering a fire-formed, neck turned only case, with the same bullet pressed at the oal setting of 2.487, I then unchambered the cartridge and remeasered, and it miked out at 2.458 inches...what should I think of this? obviously the bullet is being pushed back into the case a bit...what should I do? still use the oal guage measurement or use the chamber method? I understand that the bolt will force the cartridge down and to the right and maybe give a "false reading"? Please give me some insight on the "correct" way of determining the best way to go...I'm interested in the best possible accuracy...also there have been no pressure signs at all...thanks
     
  2. Centre Punch

    Centre Punch Well-Known Member

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    Hi nelsonic,
    I use the "Ranging Rod" method i read about in a handloaders digest many years ago. This consists of a 30" length of 5mm brass rod ( for 22c/f and 243, 6mm, etc,7mm for 308) too which i have attached a locking collar approx 1" diameter and 1/2" thick.

    Firstly i lift the bolt to cock the firing pin, i then slide the brass rod down the muzzel until it stops against the bolt face. i hold it in place and move the collar to contact the muzzel and look it in place.
    With my Vernier i measure the protrusion of the rod from the face of the collar 3 times and record the mean reading.

    The same process is then repeated but this time with the bolt removed and i have an assistant wedge my chosen bullet into the lands and hold it there with a suitable piece of dowel. The rod is then slid down the muzzel untill it touches the tip of the bullet, the collar locked and a reading of the protrusion taken and recorded as before.

    Subtract the smaller dimension from the larger dimension and this will give you the exact C.O.A.L. for that bullet.
    I then make up a dummy round to this exact C.O.A.L., take a bullet comparator reading and use this dummy round to set up my dies.

    In my opinion this the most accurate way of finding your C.O.A.L and it may be a bit of a chore to do this with every different bullet you use, but in the quest for accuracy i think it is well worth it.

    Ian.

    "I mean't to shoot the pike but the duck got in the way"
     

  3. rwleonard

    rwleonard Well-Known Member

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    Feb 6, 2004
    For hunting rifles, I just seat bullets out farther and farther until:

    1. It won't fit/feed in the mag...or...

    2. I can't fully close the bolt reliably from hunting positions (sitting, off-hand, etc)...or...

    3. When I try to extract an unfired round, it pulls the bullet.

    Once I have found the max length without on of those bad things happening, I begin load development at that length and work back if velocity/pressure/accuracy tells me I need to.

    Rick
     
  4. brian b

    brian b Well-Known Member

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    Aug 15, 2004
    nelsonic,
    I assume that you are talking about the stoney point oal guage, it is for ballpark measurement (at best) I have done exactly what you are doing and it is frustrating, the best way that I have found is to use a magic marker from just above the ogive to just below the ogive and close the bolt carefully to not get false readings,once you have found the lands just use lighter fluid or solvent to clean off the marker.
    B
     
  5. Bob S.

    Bob S. Well-Known Member

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    Sep 26, 2004
    CP - The ranging rod method sounds like it takes the reading from the tip of the bullet. Bullet length can be quite inconsistant. Have you seen the groups tighten up when you started using this method? I'm also looking to find the best way to measure overall length. The chamber method and measurement from the ogive sounds about the best to me, but your method sounds easy.

    Any other ideas?
     
  6. D.P.

    D.P. Well-Known Member

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    Nelsonoc
    The stoney point OAL will get you close. I also stand the rifle straight up and down, I feel it gives a better reading and doesn't bind. To remove another factor, I fire a round in my chamber and thread the case.
     
  7. Bob S.

    Bob S. Well-Known Member

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    rimfire - what does thread the case mean? How is it done? What factor does it remove? Thanks!
     
  8. ss7mm

    ss7mm Writers Guild

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    Cowboy:

    Sometimes a picture makes things easier to understand. This is a picture of the Stoney point guage and a case that has been modified to work on the end of the guage.
    [​IMG]

    This is the info from their web site as to the thread specs. etc.
    Q: What is the thread size for the OAL Gauge? I am an experienced machinist and would like to modify my own brass. Can you provide the proper drill bit and tap?
    A: The thread size is 5/16" x 36. This is a special size drill and tap that we can provide to experienced machinists. Contact us for details.

    What I do with mine is to use the case on the end of the guage and then I insert a long 1/4" dowell from the muzzle. This, done carefully and consistently, gives you a better feel for the contact of the bullet and the lands. With a little practice it's easy to hold the guage and case in the chamber, use the same hand to move the bullet up to the lands, against the slight pressure you have on the dowell with your other hand. You will develope a feel that will be very consistent. Do this several times, checking the length each time for an average. Also this way there is never a time when you need to get a bullet out of the lands that won't come out by gravity alone.
     
  9. Centre Punch

    Centre Punch Well-Known Member

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    Cowboy,
    I should have explained that the same bullet used for the measuring is used in making up the dummy round. a comparator reading is taken from the base of the case to the ogive and recorded for reference.
    As most bullet seaters seat against the bullet ogive, the variation in bullet length will have no affect on where the ogive contacts the rifling. Even though the actual overall length of each loaded round may be will be different because of this variation, the distance from the base of the case to where the ogive contacts the rifling will always be the same.

    This method has never failed me and is the most accurate way of obtaining OAL to the lands, it also allows you to seat any bullet any amount into the lands initially without having to use modified or fireformed cases. All my buddies have adopted this method and have remarked on how much more accurate it is over the current bunch of overall gauges.

    Ian.

    "I mean't to shoot the pike but the duck got in the way"
     
  10. BountyHunter

    BountyHunter Writers Guild

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    I have used about every method known.

    1. Jam seating long bullet "jams" the bullet about .030-040 into the lands. Not best way.

    2. Stoney point is expensive with specific modified cartridges for each you reload and tool breaks so easy.
    Got two stoney points will sell cheap.

    3. Best (most accurate) method and tool is the sinclair bullet seating depth tool ($28.95) from Sinclair int. www.sinclairintl.com. No extra $5.95 special cartidges to buy and nothing to break. Measures off the ogive and right at "touching the lands". This is the tool used by most 1k BR guys. One person can easily and accurately measure exactly where lands are and track throat erosion.

    http://www.sinclairintl.com/cgi-bin/category.cgi?category=search&item=09-400&type=store

    BH
     
  11. Bob S.

    Bob S. Well-Known Member

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    ss7mm - Thanks a picture is worth a thousand words.

    CP - Thanks, now I'm on the same page as you.

    BH - Thanks for the info and links. I might have to get one of those.
     
  12. bucknutz

    bucknutz Well-Known Member

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    Jun 30, 2004
    i use the sinclair,it gets you real close.
     
  13. Alan Griffith

    Alan Griffith Well-Known Member

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    Just want to make sure I am doing this correctly. My Rem 700 in 30-06 has such a long magazine well and leade that I never felt I could load against the lands. I typically load so that .308" or more of the bullet is in the neck. My most accurate load is either the Nosler 180 Accbond or Ballistic tip in front of 57.6 gr of H4350, Win case and lg rifle primer. My barrel is turned down to a toothpick (.550" at the muzzle) so I'm very happy when I can reach MOA or better. This load gives me that or just above with the OAL at 3.395". The past few days, I've experimented with a "range rod" technique. I take my Dewey cleaning rod with no tip on and carefully insert into the muzzle until it touches the "cocked" face of the bolt. I carefully wrap some masking tape around the rod at the muzzle. Now, I remove the bolt, insert a 180 gr Nosler BT into the leade and lightly hold it there with a shorter section of cleaning rod in my left hand. With my right hand, I reinsert the Dewey rod into the muzzle again, until it touches the tip of the bullet. The rifle is laying on its side, muzzle to the right and breech to the left. With this setup I can move the bullet into and out of the leade fractions of an inch at a time. This allows me to get the right feel of the bullet set against the lands. When I feel it is right, I again place masking tape around the rod at the muzzle. Once I remove the rod, I can measure with my calipers, the distance of the leading edges of the tape. I come up with 3.556" with a clean barrel. If I seat a bullet to 3.555" that should give me a safe margin with a dirty barrel, which I prefer to hunt with. Now, If I seat that far out, I figure I have about .200" of the bullet seated into the neck. I've read somewhere here on LRH.com that as long as you have 1/2 or .154" seated into the neck, I should be ok. I'll probably back off my powder charge 1 full grain and go to the range with a bunch of prepped cases and my Harrell's Premium powder measure and start playing around with seating depth, working deeper into the case.

    Any opinions or concerns?

    Big Al
     
  14. Centre Punch

    Centre Punch Well-Known Member

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    Hi GSSP,
    What you are doing is basically sound, but you are leaving yourself open to inaccurate results by using masking tape as a datum.

    It is quite possible for you to place your tape .005"-.010" from the rifles muzzel, alternatively you could butt it up against the muzzel by the same amount.
    When taking your reading with your vernier calipre you could depress your tape datum by a few thousandths or even by shy of your tape by a few thousandths.

    Do this twice and you effectively double your error and in the extreme you could end up .030" or more away the true dimension.

    This is why you must use a solid adjustable collars that can be locked onto the rod.
    Precise measurements can then be taken between the collars giving you a much more accurate and true reading.
    Check out this link:
    http://longrangehunting.com/ubbthreads/showflat.php?Cat=0&Number=83633&an=0&page=1#83633

    Ian.

    "I meant to shoot the pike but the duck got in the way"