From this photo that looks like an exceptional trophy pronghorn. I'm not so sure he has "weak mass", it could, but take a look at the position of the hunter's fingers on the left horn. Doesn't it look like his fingertips just get to the front on the horn surface? If so, and the back of the horn is against his palm and his thumb is nowhere near halfway on the inside portion of the horn, well then your looking at a big buck. His mass above the prongs look pretty damn good too, it certainly isn't thin or willowy IMO.