Good questions all.
1. Not too sure, but I doubt it. I'm guessing it might ignite the escaping gas and create a jet of flaming propane.
Mythbusters did a few experiements on this a while back but using bullets rather than flares - they ended up having to use incendiaries I believe.
2. Using HE as the propellant? You've got some serious issues. HE, unlike low explosives such as gunpowder, tend to detonate so fast they shatter materials. Low explosives detonate or burn much slower and so have a pushing effect (this is why they're good propellants).
You try using HE as a propellant and you've at best destroyed your weapon, at worst killed yourself with flying ex firearm shrapnel.
3. Possibly - Once again, Mythbusters (Damn they do some cool experiements) have been there and tried that. Normal bullets wouldn't have a hope. Hitting below the level of the fuel, also no hope. The round needs to travel through the gaseous fumes at the top of the tank to have a chance.
|