I think this is interesting enough to share with the .org.
I've seen all kinds of results using blanks with the M16A2, from flawless performance mag after mag to complete and total "f-you" jams. The primary problems are caused by the fact that the blank cartridges are not the same overall length (OAL) as live cartridges.
The most common jam while using blanks is when the tip of the blank cartridge jams against the feed ramp on it's way to the chamber. The cause is carbon fouling that prevents smooth sliding. Usually a quick wipe of the chamber mouth/feed ramps will fix this.
The second most common problem is under-powered blanks which will not cycle the action properly. This can be quickly addressed by yanking smartly on the charging handle, but care must be taken to angle the ejection port down to allow the cartridge case to clear the receiver. I've seen many bad jams occur when the operator fails to do this and the bolt closes on the fired case. If the case gets jammed up under the gas tube, expect to be out of the action for awhile to clear it.
The third problem is, for whatever reason, the magazine angles the loaded rounds down too far. This can cause a failure to feed no matter how clean your feed ramps are. Some troopers have been able to counter this problem by manually angling the magazine forward with their non-dominant hand. I have a couple of magazines that I marked because of their tendency to do this; they work fine with live rounds but don't come with me to training any more.
The last problem, which occurs not often, is that there's something wrong with the BFA itself. In desperate times some troopers have simply removed the BFA and converted their rifle into a straight-pull bolt action repeater. This is better than nothing.
Sometimes, troopers who are having problems with their rifles on semi-auto have solved fixed it by switching to three-round burst. I have no idea why this works but it sure isn't good for your ammo supply