My powder man shot his a little over two miles a couple years ago at a rendezvous in Utah. In the mountain west, particularly Wyoming, there are vast stretches of relatively flat, un-foilaged (or with just low sage brush) BLM (public) land where it is quite easy to find a safe place to shoot such ordnance... It does take at least one spotter down range (way off to the side obviously) with a pair of binos and radios to safely coordinate the whole affair. An undrilled ball is also a good choice for such a shot as it will fly significantly more in line with where the tube is pointed than will a drilled ball. Yes, his charge was two pounds and I don't remember the granulation but type was "A". There are very few places left in the US where such shooting can be done safely. His mortar looks like a seacoast with wall T's very close to the bore D and is made from a good steel alloy (100KSI yield or better). He loaded the powder chamber and then placed tubes of BP in a star ( * ) pattern in the bottom of the bore fanning out from over the powder in the chamber. Distance is easily measured with a handheld GPS unit and a 4-wheeler to get there. The spotter is required to both assure the landing area is clear as well as locating the B-ball for measuring and retrieval. His distance was 2.107 miles.
It can be done safely... the people and the equipment in the original post IS/ARE NOT. The biggest issues are having enough of the right kind (clear and flat) real estate and a tube built to withstand the pressures on the walls and not just in the powder chamber. Safely doing stuff like this also mandates knowing the kind of pressure the equipment may likely have to withstand (see BP Ultimate Pressure thread by keith44) if you want to be alive to do it again sometime. Powder man did destroy the mortar bed with that shot however so making it a habit, even under the right conditions can get expensive. He's the same guy that sold the BP bowling ball mortar to the guys on History Channel's Pawn Stars.
