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  #11  
Old 08-02-2020, 09:54 PM
K22 K22 is offline
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Understood.
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  #12  
Old 08-03-2020, 12:32 AM
Hammerdown22 Hammerdown22 is offline
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http://corbins.com/design.htm
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  #13  
Old 08-03-2020, 01:08 AM
K22 K22 is offline
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Quote:
Originally Posted by Hammerdown22 View Post
Thanks Hammerdown, I've bookmarked that one.
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  #14  
Old 08-03-2020, 04:52 PM
Daryl Daryl is offline
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Corbin's words on dish base and cup base.

"The dish base (DB) design is generally used to provide a very slight outward expansion of the bullet during firing, by vectoring a small component of the gas pressure at a slight angle to the bullet centerline. This can help "seal" the bore when the bullet is used in undersize or unknown size barrels and prevent gas cutting. It seems to have little or no effect on accuracy other than improving it in an oversize barrel. It can also be used in a rimfire 6mm jacket to help apply more localized pressure, during core seating, to the edge of the jacket and thus expand it better, removing as much of the prior firing pin dent as possible. Dish base bullets have a slight concavity, going from edge to edge without a margin, and typically using a radius of several times the diameter to produce a very shallow curve, usually less than 1/10 of the caliber.:

"The cup base (CB) is typical of paper-patched lead bullets, but can also be used with a jacketed bullet. It has a radius cavity that is less than half a caliber deep, starting after a margin of from .010 to 0.030 inches (typically about 0.020) from the edge of the bullet. The margin gives the bullet edge greater resistance to expansion at the muzzle, and is designed for the range of muzzle pressure expected. Thicker margins work best with short barrels and high pressure loads, thin margins work best with longer barrels and lower pressures. The problem with a very thin margin and a high pressure at the muzzle is that at the moment the barrel is "uncorked" by the bullet passing the muzzle, the pressure is supported momentarily only by the thin walls of the bullet base. The pressure can expand the base excessively, even to the point of cracking it apart."
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