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Old July 20, 2018, 02:21 PM   #26
BobbyJ
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Brian Pfleuger,

Thanks for the information good stuff!

Question, when you put too much powder in the cartridge why does it not just shoot the bullet out faster vs blowing up sideways? Seems the path of least resistance is out the barrel.
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Old July 21, 2018, 06:04 AM   #27
Bfglowkey
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Pressure is a funny thing. Barrel diameter and the bullet blocking it while it travels out while seems fast to us, in the pressure world is an eternity and not fast enough to bleed off the access. The speed at which pressure builds on fast burning powders is phenomenal. Think about how big a 223/556 round is and then imagine 60k psi.....to put it in perspective a C5 cargo jet loaded to Max 840k sitting on concrete ramp exerts roughly 1/32 of that per tire(28 tires total) ....now focus all that pressure Into a much smaller area. You get the picture.
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Old July 21, 2018, 10:28 AM   #28
Brian Pfleuger
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Quote:
Originally Posted by BobbyJ
Question, when you put too much powder in the cartridge why does it not just shoot the bullet out faster vs blowing up sideways? Seems the path of least resistance is out the barrel.
Time and momentum.

Simply put, there's simply not enough time for the bullet to get out of the way.

In open air, gun powder burns relatively slowly but under pressure, the entire charge ignites and builds to maximum pressure in fractions of a millisecond.

In high-powered rifle cartridges, the pressure goes from 0 to 55,000, even 65,000 psi, in maybe 0.2 milliseconds. In that time, the bullet only moves an inch or so. That's under normal conditions.

Gunpowder burns faster under higher pressure (generally speaking), so an over-load creates what you might see as a "run away" reaction. More powder makes more pressure, more pressure makes powder burn faster, faster burn makes higher pressure because the bullet has even less time to get out of the way.

The process is highly complex, and that description is overly simplified but it hits the main points. You can think of a gun barrel and bullet as a bottle and cork, except this cork has to travel a ways before it can "uncork" the barrel. If the pressure rises beyond what the structure of the steel can handle before that happens.... BOOM!
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Old July 21, 2018, 08:10 PM   #29
BobbyJ
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Yea that makes sense, some great explanations on the overcharged loads.

Its pretty amazing how intense each shot is. 65,000 psi! crazy.

My buddy bought a new Bmag .17 cal rimfire. They develop psi of like 33,000 psi. He got a hot load from the factory and it blew up. Well what happened is the edge of the casing blew out. The guns bolt only covers 1/2 of the rim and bottom half of the rim is fully exposed. It was engineered to fail that way in case of a hot load.

So most of the pressure blew down towards the magazine. It blew off the mag, the trigger, the trigger guard and his hand. He did not loose any digits but he said he was afraid to look as it felt like it had been hit with a hammer.

That was a safe explosion, I can imagine ones where there is no exit valve the entire chamber must blow like an M-80.
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