Central to this NYTimes blog post are two videos taken at Colt Defense’s testing range:

"The first video shows an M-4 being subjected to an intensive sustained-firing test. The rifle used is the standard M-4 with a standard barrel. The weapon is secured on a bench and fed one full 30-round magazine after another without rest beyond the time it takes to replace empty magazines with full magazines"


...[second] "video shows the same test with an M-4 equipped with a thicker, heavier barrel, which is used on a specialized carbine, known as the M-4A1".


http://atwar.blogs.nytimes.com/2010/...-m4a1-guns/?hp

Konrad.