I watched my best friend stick himself with an 18 gauge. I had to keep him from passing out. It may have been the funniest thing I have ever seen in my entire life. The thing was a harpoon
I'd rather not discuss it, but I will say this: Running an "un-controlled" experiment on oneself and another mammalian speice is often not the best course of action when attempting to corroborate studies.
Back in the days I had to shoot with a 19 gauge. It looks awful, but the pain is even less than with 23 gauge. I think the 19 gauges were sharper than the thinner ones.