Welcome aboard. I find just the opposite with bullets - that good jacketed bullets are superior to cast for deer. I now prefer the Hornady XTP designs, they expand very well at low velocities.
It is true that some jacketed bullets do not expand well - this was particularly true in past years before the current crop of excellent handgun bullets. This is one of the reasons that cast bullets with wide meplats got such a good reputation versus jacketed bullets in the past - old jacketed bullets didn't expand and with small meplats didn't kill well. That is not the story today. I used LBT designs in my .44 and .45s, but the best cast design performance-wise was the Lee 45-250 FN. This short bullet had a very wide meplat and killed small deer well, although I still prefer good, proven jacketed designs. But if you prefer cast bullets and they work for you, by all means keep using them!
