There are two possibilities for shooting cum without an orgasm. The first is when you perform the complete sexual act (or j/o act) concluded with a full ejaculation but during which you don't feel an orgasm. That is a condition named anorgasmia and is mostly attributed to psychological factors such as stress. The other possibility occurs when you are extremely aroused and have probably been edging for a while, so it may well happen that, right before the climax, you are unable to hold back and some semen is expelled (along with your precum or by itself) before you actually reach orgasm a few seconds later.
I've experienced both situations in the past. The first one happened to me frequently during my early 40s when I was under a lot of stress in my job. I happily ovecame that, with anti anxiety meds. The second type has happened to me only rarely and it's merely accidental.