As related to me, carbon fouling with the earlier powders in the cartridges caused a lot of problems in combat. Later ammo had a different powder with less residues, and made the rifles less likely to fail to function in a firefight.
@Smokin Joe Truthfully,mine never failed,and neither did any of the other M-16 variants like the CAR-15's that some people preferred. Seems like about half the guys in SOG carried either AK's or RPD's,though. Especially the RPD's with shortened barrels,flash suppressors,and drum magazines. Lots of these teams also work black fatigues and NVA web gear,too. Most of them thought it might give them the second or two they needed to open fire before being recognized as Caucasians. I understood that,but was more concerned with the helicopter door gunners that picked us up confusing us with NVA and opening fire on us on extractions. After all,none of them were SF or really knew what we were doing.
These guys really got screwed in one respect. Everybody in SOG were volunteers that knew we were going into Laos,Cambodia,and North Vietnam in sterile fatigues with no ID's,but those poor helicopter crews (other than the pilot and co-pilot who had to know because they had maps) had no idea where they were going on what might happen to them if shot down and captured.
Or they weren't supposed to know,anyhow.
The guys at CCN were usually (always?) inserted by USMC helo's,and I have been told a lot of the Force Recon Marines were always bugging them trying to get out on missions with the SOG guys. I even heard rumors a few of them did get to strap hang,but can't verify this. The Marines,of course,still wanted to carry O3 Springfields. <G>