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How to get seating depth using your chamber?

Discussion in 'Handloading and Reloading' started by scythefwd, May 27, 2010.

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  1. scythefwd

    scythefwd Member

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    Guys,
    I'm very new to this, but I want to make sure I am doing this correctly. I want to seat my bullets just .003 of the lands/grooves. I am sure that the chambers I will be doing this to are a little loose (I need to get one go/no go gauged because I think it might be out of spec) in the tolerances. How do you guys go about determining how long your bullets can be? Do you flare a case mouth and put it in the chamber using the lands to seat the bullet and then back off from there? Are you making castings of your chambers and measuring? I haven't started assembling, just case prepping but I am curious.

    Thanks
    scythe
     
  2. dagger dog

    dagger dog Member

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    You mention flaring in your post, are you shooting a handgun? If yes I have never heard of anyone seating "off the lands" for a handgun.

    May be you're shooting cast lead rifle bullets so you do have to flare for those to keep from shaving lead.

    The proceedure for a bolt rifle is to use a fired non flared case and slightly push the side of the neck against the edge of the loading bench until there is enough tension to hold the bullet.

    Use a black magic marker to color the bullet. Push the bullet in the case mouth just enough to hold it, chamber the test round and slowly close the bolt.

    This will push the bullet into the lands. Carefully open the bolt and extract the test round, you can see if the bullet was pulled back out of the case because it was blackened , see if this happened, if it has push it back in the case up to the line where it was originally and measure the OAL and record this number.

    Do this several times to make sure you get the average and then subtract your 0.003" off the lands and that will be the seating depth for that particular bullet, if you change bullet design you will have to do the proceedure for that bullet.
     
  3. scythefwd

    scythefwd Member

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    thanks

    I'll be seating both lead and jacketed, but mostly lead for the rifle I have in mind.
     
  4. sourdough44

    sourdough44 Member

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    I have a tool where you put it down the barrel & measure to the bolt face, firing pin cocked. After you set that measurement you take the bullet in question & hold it into the chamber, right against the 'lands' with the eraser end of a pencil. That distance is the max OAL with that type of bullet in that chamber, where it will contact the rifling. I then compare to any factors like mag length & the 'book' numbers & back off a tad for small bullet variances. I have found that even 2 guns that are 'identical' can/will have slightly different chamber lengths. I bought my tool from a guy who I don't see selling them anymore.
     
  5. 243winxb

    243winxb Member

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    Take a fired case, pinch the mouth closed just a tiny amount to hold the bullet. Put dummy round in the chamber using the lands to seat the bullet and then back off from there, measure COL. Do this 3 times or more till you get the same measurement a few times. To seat lead in rifle you will need a Lyman "M" die to bell the case mouth. Lead bullet types for rifles, some are bore riders, some not. It would help to know what caliber/rifle your going to load for.
     
  6. Walkalong

    Walkalong Moderator

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    Neck tension needs to be loose enough to let the bullet slide back in the case when chambered, but tight enough to pull the bullet back out of the lands without moving in the neck.
     
  7. USSR

    USSR Member

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    Hornady sells the old Stoney Point O.A.L. Gage, which is a tool designed for just this purpose. However, I would not recommend you try to seat your bullets so you are .003" off the leade. Even the best of bullets can have ogives that vary as much as .010", and if you try to seat your bullets at just .003" off the leade, you will end up with some bullets seated into the leade, which will do nothing for you accuracy-wise.

    Don
     
  8. scythefwd

    scythefwd Member

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    243 - the lead will be for a .30-30, fmj / spiterzers for .30-06, .308
     
  9. Fatelvis

    Fatelvis Member

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    You can achieve this by sizing the neck in your sizing die as usual, and then slit the neck with a dremel tool from the mouth of the case to almost the shoulder.
    This will allow the bullet to be gripped, but also allow the bullet to slide backwards, into the case, when forced intp the rifling when chambered.
     
  10. 243winxb

    243winxb Member

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    scythefwd , This gas checked bullet works well in 30-30 30-06 & 308 with IMR 4895.Bullets get sized to .310" or .311" depending on the rifle used. [​IMG][/URL][/IMG]
     
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