[Theme Horse Support Team]

Hi sgeorge,

While creating gallery i think you have choosen the thumbnail size. So you are getting smaller size.

Just view this below screenshot and select the full size image. You make the thumbnail size to full size image.
http://awesomescreenshot.com/0855oyq1b4

Actually your image is also not too big. This is WordPress default gallery. So you need to upload a large image to have full size display. (recommended size image width; 1440)

Thank you!