Blowing your load, but producing no sperm that is capable of impregnating a woman.
"Man, we've been trying to have a kid for ages, I'm shooting blanks at the moment."
Q: "Didn't you use a rubber?"
A: "Nah, I'm shooting blanks."
Sending a blank text message by mistake, or due to a phone malfunction of some kind.
Man 1: "Damn it, I keep shooting blanks! I can't wait for my plan to expire, so that I can get a new phone with a WORKING keyboard."
Man 2: "Man, I wish I had that problem with my girlfriend, but I wouldn't re-up until I'm at least 30."
Man 1: "I take it that you started praying for false positives?"