I guess that I will start off with a bit of history and why this is of significance. About 3-4 years ago I started casting bullets for 30-30, 44 mag, 357/38, and m/l. I had pretty descent success with 357/38 bullets and the ones for m/l. But not so great of success with 44 or 30-30. Well, I now have an older Glenfield/Marlin 30-30 and it seems to work much better with my 30-30 cast bullet loads. I also have an older 44 Mag Marlin that I have yet to try them in, but that will come soon. What could cause such a difference? I am even using the same bullets that I worked up from 3-4 years ago, so it isn't a difference in loads or materials. Do lead bullets get harder with time?