Re: Question, Not a dumb one I hope.
I'm not really sure exactly how he meant that statement. People do it the way you described all the time, and very effectively, I might add. Obviously, it's better to have dope using your setup at the exact location, but not an absolute necessity, and not always possible for every competitor. Besides which, a zero at some range is likely to be anywhere from slightly to significantly different when you change locations or shoot at the same location when the elevation, atmospheric conditions, and/or wind are different. Basically, that's what the sighters are for. So unless you've actually doped your setup at the exact location under the exact the same conditions, a "zero" will likely be slightly off and require some adjustment, anyhow.
My drop/windage cards are all based on a 100 yd zero using JBM Ballistics. I have a few different drop cards for each rifle for several places I shoot that have different elevations, and/or dramatically different average humidity and temp values. I simply dial for the predicted drop at 600 or 1000 yd for the location I'm shooting. As long as the data I input with respect muzzle velocity and atmospheric conditions is accurate, I have rarely been more than 0.5 MOA off (and usually much less) in elevation; the numbers from JBM have been VERY good.
As an example, I live in San Diego and shoot in 1000 yd matches at Camp Pendleton. The elevation at Range 117 there is approximately 420 ft. Prior to attending a match in Raton, NM, I used my known MV and the elevation/atmospheric conditions there (6600 ft, very hot and dry) to generate a drop card based on a 100 yd zero. Although I had no chance to practice there beforehand, when it was my turn at the line, I dialed the scope based on the predicted value (which was significantly less than what I normally use in SD due to the greater elevation and different atmospheric conditions). The elevation was absolutely dead on at 1000 yd, not even a single 0.125 MOA click change was necessary. Now windage, on the other hand, was a completely different story (LOL).
The most important thing is to be on paper with your first shot, which doesn't have to be in the X-ring. Of course, closer is always better in terms of minimizing the necessary adjustments before shooting for score. But as long as you're on the target, the shot marker will tell you what elevation/windage adjustment(s) are needed to get you in the center. It just needs to be close enough to get you on with your first shot because if you miss, there might be little to no feedback on which direction you were off, making it much more difficult to get dialed in. For me, JBM ballistics has been extremely close and I've had no trouble using the approach you described. So having good dope for your setup at a specific location is always the best, particularly with only two sighters per match, but not an absolute necessity.
Also, at some matches that allow only two sighters, you may be allowed two fouling shots into the berm prior to the sighters before the first match. If so, you can definitely use them to your advantage to see how close your setup is (POA to POI). Pick a dirt clod, rock, or other point, and you can start to dial in based on the actual point of impact relative to that. That way, your sighters can be used more for "fine tuning", rather than a gross adjustment. You should definitely get out and try it and best of luck.
