There are few things more disappointing than for a hunter to wait all year for an expensive hunt, spot his game, estimate it as a prize, shoot it, and then come up to find that he has downed a scrawny trophy.
Game Size and Hunting Area
Perhaps the biggest difficulty in assessing the size of big-game animals has to do with the area which produces the game. A game animal is largely a product of what it eats. With many species, the ranting of the young produces later adult animals of small size. This is especially true of deer. Antler development is determined by the incidence of certain minerals found in the game area. Deer need forage from a region high in limestone deposits if the antlers are to reach prodigious size.
Methods of Judging Game
Despite the difficulties, there are ways of appraising game before it is shot. With observation and practice, these ways will pay off, and any hunter can become reasonably adept in using them.
Two of the best tools for estimating game are binoculars and a spotting scope. With them solidly set up, the hunter or guide can often make a fair judgment of the size and desirability of game at great distances. This not only saves time spent in wasted stalking, but prevents disappointment after the kill.
Such pre-assessment should, if possible, be done in advance of the stalk. Game will be farther away, it is true, but will often be standing or slowly moving. It is hard to estimate game breaking cover at close range. Under such a situation, the hunter has to make up his mind awfully fast.
Antelope
Antelope are among the smallest of North American big game. There is a basic rule in antelope estimation - horns always measure less than they appear. This illusion is augmented by the habitual appearance of mirages in antelope country. Mirages, by their very nature, tend to extend any standing animal's height.
The basic method for appraising any big game's headgear is to compare the antlers or horns with the beast's body size. The antelope hunter who does this, and knows in advance the dimensions of an adult antelope, will come fairly close in his estimation of horn length - as long as he doesn't let the factor of desire affect his judgment.
Adult male antelope average 34 inches long and stand 36 inches high. Hog-dressed bucks will lose an average of twenty-seven per cent in weight. As an example, two of the biggest bucks checked at a nearby station for a 1960 Idaho special antelope hunt weighed 90 and 95 pounds respectively. That meant a live weight of 123 and 130 pounds.
In today's hunting, a 15-inch antelope is considered mighty good. Most good trophies will be in the 13-inch class. A 13-inch buck should have horns which appear to be at least one-third the animal's body length.
Mule Deer
Because of their variation in size between areas, deer are hard to estimate as to antler dimensions. First, the hunter should predetermine if the general run of animals in the region he wishes to hunt is large or small for the species. Then, as with other game, a comparison of the headgear may be made with the beast's body size.
One thing I've come to look for when sizing-up trophy mule-deer bucks is the amount of width between the antler and the body, as seen when the beast faces either away or towards me. Big muleys in many western areas will have a rump width of around 18 inches, hair and all. If, as the animal faces away, there appears to be half that much width between antler-and-body on the outside, then it is in the 30-inch class. This trick is most useful when hunting in snow, as such a space shows up well.
Sizing the game you are hunting should be made a lot easier with these tips. Good hunting!
Source: http://www.therealarticles.com/Article/Hunting--Be-Sure-to-Get-the-Trophy-You-re-Looking-For/154242