[ame="http://youtu.be/dy9tIABsauM"].357 test video[/ame] Underwood .357 158 gr Hex plated fired from 4" S&W Model 13 through four layers of denim into calibrated gelatin. BB calibration: 585.0 fps, 3.1" Impact velocity: (err) Penetration: 27.5" Retained weight: 157.7 gr Expansion: None A few notes on this one. It was overcast, making it difficult to get a good velocity reading. Underwood advertises 1,475 fps for this load and their claimed velocity is usually very close to actual. One shot curved and left the block on the bottom, the other came very close to exiting the block on the top. I cannot say for sure whether there was expansion on the shot that exited but based on the dramatically larger stretch cavity, I think it is likely. Nevertheless, this bullet is at least capable of failing to expand. Recoil was mild for a .357 mag. [ame="http://youtu.be/3KbLafCnrH0"]10mm test video[/ame] 10mm Atomic 180 gr Hex plated fired from 4.5" bbl EAA Witness through four layers of denim into calibrated gelatin. BB calibration: 585.0, 3.1" Impact velocity: 1,251 fps Penetration: greater than 17.7" Retained weight: N/A Expansion: N/A Both shots experienced significant fragmentation and deviated, exiting the side of the block.