From the pictures, what you have doesn't look like bullets to me, although they could be cut up bullets used for something else. Are the marks on them caused by the tumbler? If not, do you think those marks resemble tooth marks. Could be a pain bullet or other lead item where some poor guy had an arm or leg sawed off and was biting on it. Also, I have a round lead bullet that looks like an Indian pounded on it with a rock to make it smaller so it would fit in his gun. I say that only because of the context in which I found it, among other Indian artifacts. Other than that, fishing weights? Actually it's a rather tough call.