Now that I think about it, there was another unauthorized shotshell modification that we tried a few times.
When we'd do shoots out at Ft. Lewis, the range that we used was also used for less-than-lethal shotgun shoots. We'd find these rubber projectiles all over the place, the kind that looks sort of like a blunt dirigible with stabilizing fins on the back. After we grew bored with throwing them at one another we came up with an idea: why not pop the crimp on some 00 buck, dump out the shot and jam one of these puppies in there?
It worked, sort of. Even with everything stripped out except for the powder and the wad over it, the projectiles were just a bit too long to recrimp properly so there were some issues with chambering -- it took a firm hand to get those Mossbergs into battery with a cartridge that long. Some preliminary testing showed that the powder wasn't burning right (insufficient pressure, most likely) but those rubber projectiles flew straight and hit hard enough to dent vehicles and punch holes through plywood targetbacks at 25 yards.
Another bit of fun occurred after the DoE borrowed our range for a few weeks. They were training with MILES gear and had a lot of blank ammunition left over which they turned in to us for disposal. Merely capping blanks off (even outside the LPO's office window while he was trying to nap) ceased to be fun after a while. We found that a large wad of toilet paper, soaked with water and rammed down a shotgun's muzzle with a cleaning rod and seated over a blank, turned the shotgun into what may very well be the most powerful spitball launcher the world had ever seen. As these "spitballs" would crack cedar shingles at 10 yards (about the limit of its effective range, due to inaccuracy) its utility was probably fairly limited. We did some experimenting to try to come up with a more accurate projectile but it never did pan out.
While not shotgun-related, there were some unauthorized cartridge modifications performed during my last few deployments. We had an issue with smaller ships not wanting to get close enough to receive our shotlines during UNREPs. The book states a maximum range of 95 yards; a knowledgeable shooter with the right wind could probably go out a bit past 100. Some of these ships wouldn't get within 150 yards. After a few missed shots they'd complain, our captain would complain, threats would be made, feathers would be ruffled, and the ship would finally get close enough. After getting yelled at enough times we got tired of it and began modifying our 7.62mm grenade launching cartridges into an "extended range" format. (Procedure: pop the crimps on two cartridges, empty half of one into the other, recrimp it, and pray.) This solved the problem. It was rather rough on the shooter's shoulder and probably the rifles as well. It's a testament to God's love of fools and the durability of the M14 that no one was injured and no rifles were destroyed by this.
Later, we came up with a design for a .50 BMG line throwing system on paper utilizing some trickery, pulled down ball ammo, and an M2. This didn't go over too well with the chain of command and it never went past the idea stage. (It probably would have worked, but I wouldn't have shot it personally. Maybe with a lanyard from cover, but certainly not standing behind it.) Our idea for a 25mm linethrowing kit ("Half mile UNREPs" was our motto) didn't pan out either.
The idea about fixing a shotline to a Sea Sparrow was pure idiocy but it reflected our aggravation with the situation and, with strong enough shotline, it theoretically would have worked.
Along the same lines, we discovered that a beverage can fits nearly perfectly into a shotcup for launching shotlines; a slathering of silicon grease on the outside tightened it right up and made an airtight seal. At nearly the same time we figured out why there's a metal pusher plate in the base of the rubber projectiles: a 7.62mm grenade launching cartridge hits damned hard, harder than an aluminum can could take. That incident was later referred to as the Soda Shotgun.
There was also the CO2 canister mortar that the HT's assembled but as that wasn't a powder burner it won't be discussed here. It was pretty damned cool though. (Get it? CO2 = cool? Nevermind.)
