Interesting. Seven shooters at Memorial Day event firing the traditional 21 shot salute were cycling their rifles manually. Special rounds that won't cycle the rifle?
At my grandfathers funeral there was an honor guard from the Air Force that fired off a salute and they had to manually cycle the rifles. IIRC there is a modification to some "ceremonial rifles" that require manual cycling, however it may just be that without a bullet there isn't enough pressure to cycle the action.
When they use blanks in training they use what's called a BFA (blank firing adapter) to hold the pressure in the barrel to cycle the bolt. All the gas just escapes out the barrel without it.
The AR15/M16 rifle will not cycle with blanks unless you have a blank firing adapter(BFA) attached. Sometimes it doesn't work with them attached. Manual cycling works every time. They also detract from the appearance of the rifle, so some details decide not to use them.