I actually did this morning in the shower. Jerked off to coming and never got hard. It happens. Just like having an orgasm without coming. That happened in the shower too. Using a narrow water force from the nozzle on the tip of my dick. Got so aroused that my legs started shaking and I had an orgasm. I was sooo excited I immediately told me wife I had dry orgasm. It was wonderful.
I remember a guy I hooked up with for an afternoon of mutual oral sex that wasn't able to get raging hard but still provided me with a rather large amount of cum. His cock was about 8" in length after sucking on it for 30 minutes and thicker than any cock I'd sucked on before. It was actually very enjoyable sucking on his semi-hard cock because if it was able to get raging hard, I doubt I would have been able to swallow the entire thing.