I cant feel it.
I can feel the penis jerk someimes or spasm.
But no, the vagina doesn't feel fuller or warm or anything really.
I think the vaginal walls are already so warm that the heat difference would be nil or negative.
The walls of the vagina are actually quite thick, so unless your shooting at a really forcefull rate, I doubt many women could feel it.
I know some women say they can, but for me, it is the jerking and spasm, the moaning, the "I'm cumming" and the dragging of the swollen head of the cock that I can feel rather than the ejaculate.