As I wrote before reading here:
A "squib load" results in one or more bullets stuck in the barrel. I've seen a revolver barrel filled with squibs. When there was only one, we'd shoot them out with a factory round.
Sometimes, the barrel would respond with a internal swollen spot. I don't think the bullets even touched each other!
The earlier "misfires" on the movie set could have been squib loads, and in trying to clear them, a good round had just been loaded.
The rest is history. Just a possibility, given the lack of investigation releases.
https://youtu.be/ff4jI-MSnmg
“Oftentimes, a ‘squib load’ will deposit [granulated] gunpowder behind the stuck bullet. Technically, the pressures built up by any subsequent fired bullet will ignite some (or all) of that powder...A ‘squib load’ results in one or more bullets stuck in the barrel. I’ve seen a revolver barrel filled with squibs. When there was only one, we’d shoot them out with a factory round.
Sometimes, the barrel would respond with a internal swollen spot. I don’t think the bullets even touched each other!...” [Does so, post 14]
Great posts all; partly true in many cases.
I was a cadet at a federal service academy in the early 1970s. After leaving active duty in 1999, I worked for 13 years for a small family-owned delearship in gun repair and manufacture of small parts.
When I was a cadet, we were issued M1 Garand rifles, mostly for drill but we fired blanks from them during field training each summer. Safety training was sketchy at best. Several cadets were severely injured when blanks were fired at them at close range; one guy committed suicide by loading a blank and dropping a pencil down the barrel from the muzzle, then pointing the muzzle at his chin and pulling the trigger.
Safety rules were tightened to forbid any cadet aiming a blank-loaded rifle at anyone - no matter what the range.
Blanks contain all the potential energy of a live round in their propellant; the bullet of a live round is merely an object made of suitably dense material with an aerodynamic shape (more or less) that will carry the chemical energy released from burning propellant to a useful range - as kinetic energy.
Blanks are just as lethal at close range as live rounds. All safety rules for gun handling apply. Everyone on a movie set ought to be trained in gun safety and quizzed at random intervals; anyone flunking the quiz ought to be summarily fired on the spot. Willful violations ought to bring fines or legal action.
US military blanks (M1909 for Garand; I forget the nomenclasture for 7.62 NATO) were sealed with a card wad, then coated with red lacquer. It is barely possible that a fragment of wadding could be shot forth, to injure a person. But the range must still be relatively close.
In my capacity of gun-repair tech (not a gunsmithing school grad), I saw many strange examples of poor gun handling or damage: local police bought us items to deload or fix all the time.
Bullets lodge in the barrel because there is insufficient gas pressure to expel to expel them. Sometimes a weak load can be detected by the abnormal sounds emitted on firing, but if the shooter isn’t focused on the gun, these clues are often missed. Firing lines at pistol matches are such busy, noise-filled, distracting places.
As a repair tech at the gun shop I saw several revolver barrels with four or five bullets stuck. Barrels bulged, or split. Auto pistols were thus damaged less often, but many years in the past our founder did obtain a barrel from a Colt’s M1903 Pocket Hammerless 32, with bullets stuck in a line, stacked from muzzle to leade. It did split.
Barrels so mistreated often get an external swollen spot or bulge. Inside they get an open area below the bulge, often encircling the bore. Technical jargon for such damage was a “ring.” But it is possible for a ring to form in a barrel without causing any corresponding bulge outside; back in the day, this was more common in rimfires, when such ammunition was more misfire-prone, and the steel used in budget-priced rimfires was not of top quality, nor was it treated extensively during manufacturing. Sometimes, we’d discover more than one ring when the owner didn’t know of any at all.
Rings often ruin accuracy potential, but not always. The max number of rings I recall seeing was four or five. It was a low-end bolt-action 22 rimfire but I forget who made it.
We always warned shooters never to “fire out” a bullet stuck in a bore. The potential for rupture and thus injury is never zero.
The only way to reduce the number of injuries & fatalities from poor gun handling is to know the rules cold, and never turn a blind eye to anyone’s violation of them. No exceptions, no matter the miscreant’s rank nor wealth.
No exceptions.
Wrong! No amount of "pressure," alone, will ignite gunpowder.
However, flaming gases will.
Regards,