Bull, I'm not sure I should even speak to you, you ol' scoundrel, after you were here in the valley and didn't drop by for a spell. That's nudging awful close to unforgivable sin.<P>The practical value of such notes as the relative erosion rates is much greater than you imply in your post. I'm reminded of something a bit like this from my days as a wildlife biologist � the immense value of knowing the population TREND in a certain elk herd, for example. It isn't necessary or even all that useful to know the actual NUMBERs of the population, down to the last animal, if you can keep a good eye on the trend of that population. You know what the environment is like, how the habitat is doing with approximately x,000 elk. A trend count that indicates about a ten-percent increase, say, is good enough to help you decide other matters relating to the size of that population. It doesn't matter so much whether the base population you started with was x,000, x,050, or even x,100 individual elk. They're not going to be managed or marketed like livestock. They have to be managed as an entity of an approximate size, not as a property asset.<P>The value of this erosion relationship to a designer, or to a shooter comparison-shopping for a cartridge choice, is not so much how much more or less rapidly Chet's barrel erodes than Charlie's barrel, but how much faster or slower A barrel WOULD erode IF IT WERE another caliber, in any lifetime of shooting. There's no point in studying the effects of any factor, in any field, if you don't at least try to isolate it to see what its effects are, apart from the effects of other factors.<P>The value lies in knowing which factors influence erosion, and how. With that nailed down, one can then go on to study another factor by isolating it.<P>One of my next studies, for example, will be to find out whatever I can about how much of a difference the level of maximum pressure affects erosion. I know qualitatively that peak pressures around 60,000 lb/sq in. erode throats faster than peak pressures around 50,000 lb/sq in. But HOW MUCH FASTER, I don't know. To find out, it'll be necessary to look into the matter in terms of how maximum pressure affects erosion when all other factors are identical � in a single given bore size, for example. "When all other factors are identical" is a term of comparative conditions, not what we know or expect typical life situations to be like.<P>It's one thing that makes the task of designing an experiment so tough. And so vital.<BR>
