I was a groupie wannabe machine gun guy, helped a good friend over the years with grunt work to get a little trigger time with his collection. Using the 1919A4/A6 as an example, it usually was the worst to clean. Using mil spec MG ammo,linked M1 tracer with M2 ball (ball powder), they would run a lot of rounds before stoppages began from carbon buildup...but if he used non mil spec, loaded with god knows what powder, the carbon fouling was less, but the copper load would go up. Eventually with just a pocket magnifier you could see rough raggedy, jaggedy copper stripping. Since an MG is meant to have a pretty good dispersion anyway, we never checked accuracy. But my friend and others surmised that maybe the double base WC852? powder kept the copper from adhering to some extent.
It would be an interesting experiment, now that we have borescopes. Anecdotally, I am fairly certain that BLc-2 makes cleaning a breeze in my .308, 7.65 and 8x57.
