I have been reading alot on this topic and from what I gather Bullet fit is important, because gas leakage around the bullet will cause it to melt the bullet and produce a lead spray. If you don’t have a good fit, then all other attempts to minimize leading are really a waste of time. I am not an expert but I have read this in alot of articles. If you meant maybe your bullets are smaller than your bore this could happen and you still need to have the things hammer talked about to reduce it also.