I did some tests in the late 80's using Hot-Shot nipples on my .69. With the hot-shots, I found velocity variations almost trippled, to 25fps & over in a 6 shot string. With solid nipples, the shot-to-shot variations remained 10fps or less. On target at 50yards, group sizes also doubled with the hot-shots. I didn't test it at 100yards with the Hot-shots. I discarded them.
: I used the Davis English lock on my rifle, and with solid nipples, it only allowed the caps to expand enough for easy removal with heavy loads. With light, 3 dram charges, I needed to flip the cap off with the back edge of my patch knife. I tested the Hot-shots just for the ease of cap removal. Due to the poorer accuracy, I went back to normal mipples.
: Perhaps your testing will prove more positive. Guns do vary.