re: Small caliber deer rifle recommendations?

Downshift, Very interesting idea. I've never really considered that. I did a bunch of science fair projects w/ my son where we chronographed bullet penetration vs velocity w/ Nosler BT bullets shot in a 308 Win. If you have problems getting ballistic gel, you could instead use water soaked bundles of newspaper. One thing I know you'll find is that when shooting an expanding hunting bullet like the NBT (w/ the bullet weight constant) penetration will decrease as velocity increases. I remember the 125 NBT penetrated as much as 14" @ muzzle velocity of 2200 fps, but only 10" @ mv of 2650 fps.

If you handload or know someone who does, you could always load the muzzle velocity down so that you could shoot the target at 10 feet instead of 100 yards. For example if the bullet is velocity at 100 yards is 2700 fps, reduce the load so that your test round muzzle velocity is 2700 fps, then shoot the target at close range (10-15 feet or so).