Approximating a Trophy Cape buffalo
While in South Africa I was fortunate enough to see a very fine Cape buffalo bull. According to Craig Boddington, the width of the horn can be estimated with a fairly simple rule of thumb. That is, when the bull is looking at you with its ears spread out fully, the distance from ear tip to ear tip (regardless of the overall size or age of the buffalo) is approximately 36'. The key here, of course, is veiwing the bull with its ears spread fully.

A 40" bull (or larger) is often considered a trophy Cape buffalo (as long as it has a good boss...more on that later), so it stands to reason that if the horns of the bull are apparently wider than the ears, then that bull is probably a 40"+ trophy bull.

Below is a series of photographs that I took on my first trip to Africa. I have zoomed up on the buff to give you a better view. Assuming his ears are fully spread (36"), what do you think is the measure across his horns?

Assessing the Boss
I am no expert on this, but what I have learned is to also look at the boss as well as the width of the horns. In my estimation, the buff pictured above has a fine boss indeed.

Drop and Curl
Lastly, I have learned to look at the degree to which the old bull's horns drop and curl. A trophy bull (or perhaps I should say record book Cape buffalo) will have a substantial drop and curl. In other words the horns will not look like that of a Texas longhorn or bison.