What angle of elevation yields the longest trajectory? I asked my friend who is an engineer and he was quick to respond 45 degrees, and yet on some internet site I saw an "estimate" of 35. I don't understand the physics of it to make an educated choice, but I suspect air resistance has something to do with the difference? No, opinions, please. Just the facts, man (or Ma'am). I tried a search of Angle, range, with no results, so I tried.

Sierra exterior ballistics cd has the information on it. I will try to look it later and let you know what is has to say.

A 45 degree angle would yield the longest trajectory only if you were shooting in a vacuum. In practicality, the longest trajectory is seen in the 30-35 degree range.

The animated chart in your reference URL threw me for a loop earlier, as it showed the max angle for a drop BELOW the point of origin to be 32 degrees. That was the site that had led me astray in the first place. But when you watch where the projectile crosses the 0 elevation (the original elevation) at the greatest distance the angle of elevation is 45 deg.

Then I guess this is where ballistic coefficient comes in, and the higher b.c. the closer the angle gets to 45? (Thanks, guys. This IS enlightening.)

True enough for small arms. But artillery shells, which go high enough to reach very thin air, often are at or close to 45 degrees for max range.

Yeah, you really need to know air resistance to get an exact angle. Forty five degrees is correct for zero drag (frictionless). That would be true on the moon, for example. Here is an example that ends up with a little over 34 degrees yielding max range. http://www.loadammo.com/Topics/May01.htm It really depends on the bullet/gun. And of course on atmospheric conditions.

Very true. Also, need to revise my earlier statement. I just went back through my copy of Understanding Firearm Ballistics. Chapter 19 on Maximum Range states that "because of air resistance, the maximum range will normally be achieved between 27 and 35 degrees. It will usually be closer to 31."