billnpatti
Member
When I first spoke of tumbling my rifle balls in a rock tumbler, several questions about the process were posed by some of the participants. One of them concerned the possibility of the size of the balls being changed by tumbling them in a rock tumbler. In an attempt to determine if this happened, I took a batch of around 200 .50 cal. balls. I selected a random representative sampling of 50 balls and measured their diameters. To be sure that I had the best representation for the diameter of each ball, I measured it three times (x axis, y axis and z axis) and averaged them to get a representation of the actual diameter of the ball. Then I averaged all of the diameters to get an average ball diameter for the batch. I found that the average diameter was 0.4880 inches and the standard deviation was 0.001.
I tumbled the whole batch of approximately 200 balls for 8 hours in my rock tumbler. After tumbling, I repeated the same measurements on another random sampling of 50 representative balls. This time the average diameter was found to be 0.4897 with a standard deviation of 0.001. The difference was very slight and within experimental error. I concluded that even after tumbling for 8 hours, the balls were unchanged in size.
The balls were found to have a rough surface that looked as if they had been sand blasted. This was obviously due to them striking each other in the tumbling process. When tumbled for an hour or less, the balls come out very nice and round and have a very smooth, almost a polished, surface. Obviously, 8 hours is too long if you want a nice smooth surface.
One of out participants, BCRIDER, had an interest in the aerodynamics of a dimpled ball, similar to a golf ball, in flight. While the surface imperfections on the tumbled balls are not dimpled, the imperfections that are there somewhat resemble extremely tiny dimples. This raised the question in my mind of whether these balls might act differently when fired from a rifle and produce a measurable difference in the trajectory. I have my doubts that the imperfections in these balls are sufficient to alter their trajectory but it is too tempting of a project not to give it a try to see if I can measure any difference. I am proposing to set up targets at 50 to 100 yards and shoot at them using smooth balls and then using the rough surface balls. I will keep all of the factors such as powder, charge, patch material, lube, caps, etc. constant and let surface of the ball be the only difference. I will shoot from a solid bench rest. I will look at both POI and group size to see if I can tell any difference.
If anybody has any ideas for improving my paradigm, please let me know.
I tumbled the whole batch of approximately 200 balls for 8 hours in my rock tumbler. After tumbling, I repeated the same measurements on another random sampling of 50 representative balls. This time the average diameter was found to be 0.4897 with a standard deviation of 0.001. The difference was very slight and within experimental error. I concluded that even after tumbling for 8 hours, the balls were unchanged in size.
The balls were found to have a rough surface that looked as if they had been sand blasted. This was obviously due to them striking each other in the tumbling process. When tumbled for an hour or less, the balls come out very nice and round and have a very smooth, almost a polished, surface. Obviously, 8 hours is too long if you want a nice smooth surface.
One of out participants, BCRIDER, had an interest in the aerodynamics of a dimpled ball, similar to a golf ball, in flight. While the surface imperfections on the tumbled balls are not dimpled, the imperfections that are there somewhat resemble extremely tiny dimples. This raised the question in my mind of whether these balls might act differently when fired from a rifle and produce a measurable difference in the trajectory. I have my doubts that the imperfections in these balls are sufficient to alter their trajectory but it is too tempting of a project not to give it a try to see if I can measure any difference. I am proposing to set up targets at 50 to 100 yards and shoot at them using smooth balls and then using the rough surface balls. I will keep all of the factors such as powder, charge, patch material, lube, caps, etc. constant and let surface of the ball be the only difference. I will shoot from a solid bench rest. I will look at both POI and group size to see if I can tell any difference.
If anybody has any ideas for improving my paradigm, please let me know.
