In media_gallery.css there is the following code:

474 .media-gallery-detail {
475   float: left;
476   margin-right: 1em;
477   line-height: normal;
478   max-width: 70%;
479 }

I don't know why there is a max-width attribute in there, but it means that images will never use the full width of the page, even if you set it to in the image styles. Deleting this line works for me.

Comments

Hi All,

I had the same issue - below is my fix:

Go to sites/all/modules/media_gallery/media_gallery.css

CHANGE:

.media-gallery-detail {
float: left;
margin-right: 1em;
line-height: normal;
max-width: 70%;
}

TO:

.media-gallery-detail {
float: left;
margin-right: 1em;
line-height: normal;
max-width: 100%;
}

OR:

.media-gallery-detail {
float: left;
margin-right: 1em;
line-height: normal;
}