Danny,
I' d have been interested to see what the groups would have been just after firing that many rounds without the breakin procedure. I' m not saying the break in didn' t work, I' m just curious how much the shooting would have smoothed the barrel on it' s own.
I think, that after firing that many rounds without using the procedure wouldn' t have shown any improvement. Simply, because of all the copper fouling that would have occured. The firing smooths out the imperfections, the cleaning just keeps it from getting too fouled.
One thing I noticed is, cleaning got easier and easier the further into the break in period I got.
As far as the barrel being the hardest material in the equation, well no kidding. I' d hope so. But, I do also feel that the combination of heat and bullet travel can help clean up the " slight imperfections" that is common in any machining operation. Why do some of the best rifle builders fire lap, or hand lap their barrels? It' s to get rid of those machining marks. Steel is hard, but it can be scratched. If it can be scratched, it can be smoothed out.
Like I said earlier, this is all my experience. I' ll keep doing it because I believe in it, not because some manufacturer is going to get rich off selling me new barrels. 100 rounds isn' t going to hurt anything, and will hardly make a dent in the barrel' s life expectancy.