Casting question

[Tom]

I have a mold that casts an old style mine. The minie shoots really well in my reproduction Model 1855. The old style minies I am familiar with have the level surface at the top of the core pin and are not pointed. When casting with a core pin that has a level surface, I get a large number that are not smooth. Many minies have a "half bubble" or some kind of incongruity. Out of 5 cast minies, 1 will be decent but the other 4 are returned to the melt. I still cast with this mold because the rounds shoot so well in the Model 1855. I try to keep the temperature around 850 degrees. I have tried around 775 and above 900 but nothing really changes. I hold the mold at an angle and try to pour the lead in with a ladle doing my best so that the lead does not cover the hole preventing air from escaping.

Is anyone else experiencing the same thing? Do you have any suggestion? Thank you in advance.