John Boy
09-18-2009, 11:35 AM
... or asked another way - can the weight of a cast bullet be increased by varying the temperature of the melt?
Background:
I have a 38-55 mold that was designed to have a nominal weight of 330gr using 1:20 alloy. I have cast them with 1:20 and 1:30. The weights at 1:20 are 317grs (680 degree melt) and the weights at 1:30 are 326gr.
I have varied the temperature casting the 1:30 alloy from 720 to 780 degrees. While casting at 760 degrees, I had only one perferctly formed bullet drop at 329grs while the rest were 326.0 to 326.7grs with less than 10% outside the bell curve
So, the question is: to obtain heavier weights, which way should the melt temperature go - Up or Down to obtain a heavier weight bullet?
Do know that:
*** soft alloy bullets for a .375 diameter shrink .004 and harder alloys shrink less. But this bullet is used with original powder not nitro in the velocity range of 1040 to 1080 fps. Need the soft alloy for obturation
*** I can 'Beagle' the mold and the weight will increase because of the increased diameter of the bullet. But would like to get this mold to cast 'as is'
Thanks for looking and possible advice
Background:
I have a 38-55 mold that was designed to have a nominal weight of 330gr using 1:20 alloy. I have cast them with 1:20 and 1:30. The weights at 1:20 are 317grs (680 degree melt) and the weights at 1:30 are 326gr.
I have varied the temperature casting the 1:30 alloy from 720 to 780 degrees. While casting at 760 degrees, I had only one perferctly formed bullet drop at 329grs while the rest were 326.0 to 326.7grs with less than 10% outside the bell curve
So, the question is: to obtain heavier weights, which way should the melt temperature go - Up or Down to obtain a heavier weight bullet?
Do know that:
*** soft alloy bullets for a .375 diameter shrink .004 and harder alloys shrink less. But this bullet is used with original powder not nitro in the velocity range of 1040 to 1080 fps. Need the soft alloy for obturation
*** I can 'Beagle' the mold and the weight will increase because of the increased diameter of the bullet. But would like to get this mold to cast 'as is'
Thanks for looking and possible advice