TLH- I'm no expert but I have read that when the projectile isn't pressed firmly into the powder charge the air chamber can create a situation where the powder detonates rather than burns rapidly. There has been speculation over the years that a similar thing can occur with very light target loads. Some 38 Special revolvers have blown up using target wadcutter loads with little dabs of powder. Too much space in the case can cause the charge to go off like a grenade. At least that's the theory. I don't know...
Complete myth. Whoever came up with that one has a long career in politics ahead of them. "It wasn't me! It wasn't my fault! There's no way it was a double charge! It was some kind of science thing that I made up on the spot! It was global warming!"
Just for fun, try putting some confetti or something in a primed case, with no powder or bullet. Shoot the primer. Wheeee! So, we're supposed to believe that recoil can "suspend" powder, despite the fact that the primer in the cartridge
already throws powder around inside the case like that, while it's lighting it?
No, it's a simple example of two things: 1. People doing stupid or careless things (or having an honest accident, in rare cases) and then refusing to take responsibility.
2. People taking a simple rule, not understanding the purpose of the rule, and then trying to apply it to other things. For the seating thing, it
is a fact that you can blow up a rifle in a high-pressure cartridge by seating the bullet too long. That's not due to a mythical "air space." That's because, as I said, with top power loads, the bullet needs a "running start" into the rifling. If it doesn't get that, then the pressure spikes as the powder keeps burning
at the normal rate, while the bullet isn't moving. Let's say you have a nail that's magnetically stuck to the face of a hammer, and you're trying to get this nail into a piece of wood. What works better, leaning on the hammer, or swinging it? Same thing, a "running start" helps get the nail/bullet moving after it hits resistance.
This has been misapplied to all
kinds of things, however. Most pistols can be safely loaded with the bullet jammed into the rifling, because they use faster powders at lower pressures (whether or not you get a pressure spike depends on the powder, but I know for a fact that Alliant Power Pistol won't spike). If you have a stuck bullet and try shooting it out with a "blank" that's not an actual blank but a normal reduced load for that bullet, you won't ring the barrel (if you used too much powder or too fast of a powder, you'd split the entire barrel, not "ring" it); it's pretty much only possible to ring a barrel by shooting a bullet into an obstruction. It's not the gas that does it, it's the
bullet going "squish," and pushing out the barrel. Gas
physically cannot concentrate pressure and create a ring-shaped dent like that, at least not under the conditions inside a firearm.
And most importantly, it's not the air space that blows guns up. Some powders, like Blue Dot, do have warnings not to leave an air space, but that's because they burn
slower without compression, and you could end up with a squib load. I'm really not aware of any powders that actually do burn faster with an air space.
But someone, somewhere, heard that seating bullets long in a .300 Win Mag or something can blow up a gun, decided on his own that it must be due to an air space, maybe remembered from his misspent youth that M-80s only have a thimblefull of flash powder in 'em and the rest is air, and jumped to a totally wrong conclusion. Then the internet happened, and it spread faster than myths that Elvis is alive, and an alien.
