Originally Posted by SCmasterblaster
I never thought that blow-back operated firearms could be so finicky.
My understanding was they are. I have done several 'melt' jobs on my carry guns, and researched the subject extensively before putting file to metal.
To operate correctly, the weight of the slide and the return spring(s) are 'tuned' by the designer to work with a particular class of bullet weight and chamber pressure. If either of these are altered by the user, say, by using +P , +P+ or larger or smaller handloads, the gun may now be out of 'tune' and not operate properly.