Quote:
Originally Posted by Frank Srebro
I understand that bismuth would have more surface area against the bore as compared with lead (with the same weight/diameter of shot), but why would that result in more pressure? Can you please elaborate? Thank you.
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Frank, chamber pressure is created by the resistance of the ejecta against being moved forward. Resistance is either + or - by changes in the weight of the ejecta and by changes in the amount of resistance/friction of the ejecta against the barrel wall. An equal weight of Bismuth, say 1 1/4 ounce has a much longer shot column compared to 1 1/4 ounce of lead. (1 1/4 ounce of Bismuth has a little more surface area against the bore than a 1 3/8 of lead.) The larger surface area of the shot column creates more resistance through friction and increases pressure. That is why Bismuth can not be loaded using lead recipes for the same weight with an expectation of similar pressures.