How do you determine "at the lands" by your method?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by JustC, May 21, 2004.

  1. JustC

    JustC Well-Known Member

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    I use the sinclair tool to determine the OAL at the lands. I do however press firmly against the rod which contacts the base of the bullet that has been "dropped" into the lands. I am wondering if by pressing against the rod,..I have advanced that bullet into the rifling by several or more .001"s. Anyone have an opinion on this?

    Thanks
     
  2. Mysticplayer

    Mysticplayer Writers Guild

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    Mine is the low tech method. Put a bullet into an empty case, blacken the bullet with a zippy marker, chamber by hand. Keep increasing bullet length until 2 or 3 land marks show up on the bullet (most barrels have 6 lands but they are never the same distance away). The marks will show up as a horizontal line in the ink.

    I repeat, this time chambering with the bolt. If there are no differences, then this is just on the lands. If you like a 'hard' seat, just keep increasing the bullet length until marks equal to the number of lands show up around the bullet. Only the ink is removed. The bullet is not jammed into the lands ie jacket scratched.

    I don't want to jam the bullet into the lands because if I extract the case, the bullet may stay allowing the powder to spill in the action and cause a nice mess.

    Jerry
     

  3. Michael Eichele

    Michael Eichele Well-Known Member

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    I am real fortunate, my new 300 RUM has evenly spaced lands equal distances apart. I use an exception smith though. I also use the low tech method. I slightly seat a bullet into an empty case and drive it home. I then back off a couple thousanths until the land marks dissapear. Then forward 1 or 2 thousanths. Then I measure the OACL with a comparator. For each thousanth forward more I seat the bullet, that is the amount "into" the lands.
     
  4. JustC

    JustC Well-Known Member

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    gents,..I always get a rifling mark from all 5 or 6 lands when I chamber a round and then remove it (using my method) I am thinking that by me placing a fair amount of pressure against the base of the bullet (with the rod which contains the 2 stops for case head and bullet base) that the soft copper jacket has actually allowed me to push the bullet into the rifling by hand. then,..when I position the second rod stop against a fired case head inserted into the chamber, I take the distance between the 2 stops positioned on the rod,..then add the bullet length, and I have the OAL to the lands. (as per the instructions)

    Do you all think I could push the bullet into the lands by hand and therefore change my OAL measurement to one in which I have REALLY calculated an "into" the lands situation? Also,..I assume the members here would consider ANY MARK at all on the jacket to be an "in the lands" situation?

    thanks

    [ 05-21-2004: Message edited by: JustC ]
     
  5. jmden

    jmden Well-Known Member

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    JustC,

    I wonder if there is really a way to answer your question because in order to do so there would need to be a "standard" method that allows you to define when the bullet is on the lands. See what I mean? This person has one method, that person has another...the different methods are probably within a few thousandths. Without being able to visualize the bullet on the lands with some degree of certainty, for instance, or having a standard method that exerts X amount of force to the bullet to seat it on the lands, IMHO it seems a difficult question to answer. I use the Sinclair tool and the appropriate cleaning rod guide and just drop the bullet down the cleaning rod guide. Where the bullet stops, I say it's against the lands. For me, this has been my way to have a "standard measurement" from bullet to bullet and/or chamber to chamber. Not sure if it's the best way, but if a guy doesn't do things exactly the same way while taking this measurement every time, the measurement becomes less valid. For me, using the cleaning rod guide seems to take some measure of human error out of the equation that might be there othewise. Anyway, that's what I like to think. But you have a very valid question and I'd be very interested in other folks opinion on this one as well.

    Thank you,

    Jon Denham
     
  6. dbhostler

    dbhostler Well-Known Member

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    JustC;

    I used to seat the bullet in a lightly sized case but found that to be to inconsistant. I now use a Sinclair seating tool and measure OAL with a Stoney Point tool. I lightly tap the base of the bullet to make sure it is centered and yes this will no doubt force it into the lands a couple of thousands. But I don't worry about that too much because the cases are not perfect either, ie base thickness and perfectly flat.

    Len;

    I thought that most rifles retract the firing pin when the bolt is lifted? [​IMG]

    db
     
  7. speedbump

    speedbump Well-Known Member

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    I use a Stoney Point tool & average the length of three consecutive measurements. They're occasionally off by 1-2/1000, but the averaging method seems to work. I never had that much faith in the marker method, but to each his own.... [​IMG]
     
  8. Len Backus

    Len Backus Administrator Staff Member

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    Michael

    I've read of that "close the bolt" method but I have a question. When the bolt is cocked the firing pin protrudes forward. When you start a round forward into the chamber it is really the pin pushing the cartridge case forward and not the bolt face. Does the firing pin fully recede as the bolt is finally closed and before the bullet hits the lands?

    If not, isn't there more space (length) once the bolt is fully closed and now the bullet no longer makes contact with the lands?

    [ 05-21-2004: Message edited by: Len Backus ]
     
  9. Len Backus

    Len Backus Administrator Staff Member

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    db

    Duh...braindead me! I meant the ejector pin which is part of the "firing pin" assembly which should be removed from the bolt first if you want to get the most accurate reading. At least that's what I read on Benchrest Central. Haven't tried it myself. Wondering if anyone elase here has.
     
  10. dbhostler

    dbhostler Well-Known Member

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    Len,

    Yes, I have done that, to fireform brass in my 244 AK, remove it all together.

    db
     
  11. D.P.

    D.P. Well-Known Member

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    Hello Len

    Your question is one that concerned me in the past. I think I get a litle crazy with reloading detail at times but there is no substitute for consistent accuracy. I use a Stoney Point gauge, as for the shells I use ones that were fired in my chamber and thread them 5/16 36 tap. This way I know that bolt face to shoulder is snug and OAL is consistent. If you only neck size and dont bump the shoulder everything stays consistent. I guess if you use a case from your chamber the ejector wont be able to push it forward if your on the shoulder?
     
  12. Len Backus

    Len Backus Administrator Staff Member

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    Rimfire

    Excellent observation! Yes, I bump the shoulder only about .002 so you are right, the ejector position would be a non-issue.
     
  13. Michael Eichele

    Michael Eichele Well-Known Member

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    Len,

    I had the smith that built my rifle replace the factory ejector spring with a spring that is light enough to depress with your finger. It is just barely enough to throw the case. The benefit is less trouble for precision reloading and it allows easier extraction due to the super tight BR chamber I have due to less preassure on the side of the case in the chamber. I generaly dont take into consideration the firing pin. I also use fire formed cases which help a bit.

    [ 05-23-2004: Message edited by: meichele ]
     
  14. Len Backus

    Len Backus Administrator Staff Member

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    Michael, that's an interesting idea!