I've had a blocked bbl once with my M-11/9 in full auto. THAT was a bit harry! Luckily, no one was hurt. Three bullets lodged; stacked end to end near the breech. We figure a squib round went in; probably only had a primer and no powder charge. The next two forced the first down with each subsequent round. Once the last one would not let the bolt fully close, the slam-fire firing pin alerted the user when the case exploded with an open bolt! The barrels in these guns are made very robust on purpose; for good reason. When you can burn 20 rounds per second, it does not take long for mistakes to multiply.
The act of preventative maintenance, in and of itself, is FAR MORE important than brand/grade/base choices among lubes and filters.
- under maintaining something is akin to abuse/neglect; that can kill equipment by shortening the lifespan
- over maintaining something has never been proven to be anything but a waste of time and money