I have no idea whether the Marine Corp uses the M-4 carbine with any regularity or not, but the M-16 jamming easily isnot uncommonby my experience in the Army in Kuwait, Saudi and Iraq, even with a weapon cleaned one or more times a day.
I knew the piece about the 45 was suspect, as I had a Remington Rand .45 as my sidearm in Desert Storm and it was a piece of crapolie with the barrel shot out.
M-14's were being brought over to theater when I deployed with 101st in 2003, and it has alwayshad a very good rep. The .50 cal Barret is a very good rifle for taking out personal and light-skined vehicles but obviously is not going to knock out a vehicle with one shot unless you got the engine block.
Interestingcorrections by "whoever" corrected the original email.

This topic made for an interesting read. I'm not sure who is right regarding the firearms, but still interesting to read nonetheless! I never considered those reasons for the .223 to replace the .30.