https://en.wikipedia.org/wiki/M16_rifle#Reliability
The M16 and 5.56×45mm cartridge was tested and approved with the use of a DuPont IMR8208M extruded powder,
that was switched to Olin Mathieson WC846 ball powder which produced much more fouling,
that quickly jammed the action of the M16 (unless the gun was cleaned well and often).
1968年に米軍が出したレポートに記載があるらしい。画像PDFだし216ページもあるので読むのしんどいｗ
http://www.dtic.mil/dtic/tr/fulltext/u2/a953110.pdf