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Slug the barrel, or the forcing cone?

Discussion in 'Handloading and Reloading' started by easyrider6042004@yahoo.ca, Sep 13, 2008.

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  1. easyrider6042004@yahoo.ca

    easyrider6042004@yahoo.ca Member

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    1. Why bother to slug the barrel and then size your bullets to match, when the bullet has to pass through the cylinder throat before entering the barrel through the forcing cone?

    2. Isn't an oversized bullet re-sized by the cylinder throat anyway? In this case, shouldn't bullets be sized to throat diameter, or perhaps .0005 larger?

    3. Would sizing bullets bigger than throat diameter place undue stress on the cylinder, because upon firing the cylinder will have to extrude the bullet as the bullets passes through?

    4. Am I missing something?

    BTW, I tried slipping a .357 Speer JHP through the cylinder throat from the cylinder mouth.

    Results:

    1. Ruger GP100 and NM Blackhawk: Bullet passed through the throat when bullet dropped vertically into the chamber mouth. I could wiggle the bullet very slightly in the throat.

    2. Two S&W 686-3s and one S&W 586-1: Bullet had to be pushed with slight pressure needed, using a brass rod. I didn't feel the bullet wiggle in all 18 throats of 3 cylinders. I'd say the .357 Speer JHP was a perfect match for S&W throats.
     
  2. rcmodel

    rcmodel Member in memoriam

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    You are correct.

    Slugging the barrel on a revolver will only tell you the bore diameter, and whether or not there is any tight or loose spot in it. Interesting to know, but not real useful when picking a bullet sizing die.

    The real critical measurement for best accuracy is the cylinder throats.

    Lead bullets need to be sized to fit them, not the bore. Even if the throats are much bigger then the bore.

    The bullets will slug down to fit the bore, but if they start out loose in the throats, they start out crooked, and don't get any better later on.

    rcmodel
     
  3. easyrider6042004@yahoo.ca

    easyrider6042004@yahoo.ca Member

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    rcmodel,

    Thanks for your answer. It's clearer to me now.

    1. It seems that my S&W 686s and 586 throats are right at .357, does this mean that this is the correct diameter?

    2. The .357 Speer JHP bullet wiggles just tiny bit in my GP100 and BH, does this mean that I need to resize a little larger than .357?

    3. Who makes a .3575 resizing die?

    BTW, I've been wanting to ask about your "rcmodel" handle because I used to build and fly RC model aircraft which we referred to as "rc model planes". Do you by any chance fly rc?
     
  4. rcmodel

    rcmodel Member in memoriam

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    Well, the resize part only applies to cast lead bullets.

    You can't resize jacketed bullets and make them any bigger then they already are.
    (It is possible to make them smaller, but I don't recommend it!)

    Jacketed bullets for the most part, have a very soft, pure lead core.
    They will slug up to fit the throats at .357 Mag pressures.

    Of topic, but:
    My rcmodel name is one I have used since there were computers and DOS bulletin boards.

    I used to be VERY involved in R/C flying.

    I wrote a monthly column for one of the R/C mags, and did kit testing & such for Top-Flite and other companies.
    I was also president, newsletter editor, and chief cook & bottle washer for a 75+ member club for years.

    It got to be a job, and all the work & politics were no fun anymore.
    SO, I got really burnt out, and am no longer involved in R/C at all.

    rcmodel
     
  5. Walkalong

    Walkalong Moderator

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    Absolutely correct.
     
  6. 243winxb

    243winxb Member

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    Info from Lyman, follow link.

    http://www.lymanproducts.com/lymanproducts/images/Bullet%20Guide.pdf
    For revolver, auto pistols i size on the + side. My .357 die sizes to .3575" my grove diameter measures .357" Hand guns, no larger than +.001" For rifles +002" to +.003" over bore diameter. :banghead:
     
  7. rcmodel

    rcmodel Member in memoriam

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    That is only true if your cylinder throats match your bore diameter.

    On many guns, they do not.

    My Colt SAA for instance has a .452" bore with .4545" throats.

    It "patterns" .452" bullets, and shoots tight groups with .454" (.002" over bore size) bullets.

    If bullets sized .455" would go in the chambers I would use them, but they won't.

    rcmodel
     
  8. Walkalong

    Walkalong Moderator

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    You must size lead bullets to fit the throats. You would like them to be, for best accuracy, .001 or .002 over bore diameter. If they are more than .002 over you can be OK, but if they are under bore diameter you are screwed, unless you ream the throats larger.
     
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