Reducing the space between headers

I have 2 lines, both with h4. I would like the space to be smaller.

I have tried to use the code

@media only screen and (max-width: 520px) {
.post h4 {
line-height:20px !important;
margin-bottom: 10px !important;
}
}

I found that in the BulletPress WP Theme Forum.
It helps a little, but even if I set the value to 1px there is still a lot of space between the lines.
Can I do more to reduce the space?