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The original question, posted here, was: "How long does a bullet spend accelerating in the barrel of a rifle?"

I think it's safe to say the vast majority of people on this forum know that varies significantly, depending upon bullet caliber, bullet mass, cartridge propellant, cartridge primer and primer type, not to mention the length of the barrel, twist of rifling grooves, depth of the rifling grooves, width of the rifling grooves, type of barrel steel, the way the barrel was made (cast, forged, hammered, drilled, rolled, cut/lathed), and the way the barrel was heat-treated (hardening).

Having take a class or three in materials engineering, I do believe this can be reduced to some approximating equations, but some of the coefficients must be placarded. That is, they're discrete elements, which vary in steps between the above mentioned factors, such as the type of powder that was used. I'm not going to begin to dig into my college texts to derive a single equation t=f(x), but let's at least figure out which components can be parameterized and which will require tabular data. Here's my initial stab at it:

Continuous (can be included in the equation using algebraic and/or calculus equations):

bullet caliber
bullet jacket (affects friction)
bullet composition (jacket and composition affect in-barrel deformation, which affects both friction and its ability to seal against propellant gases)
bullet mass
cartridge propellant
length of the barrel
twist of rifling grooves
depth of the rifling grooves
width of the rifling grooves

Discrete (varies widely from one brand to another, and so much be introduced via placard coefficients into the equation):

cartridge propellant
cartridge primer (via make and model)
barrel make and model*

*barrels: So many factors go into making a barrel that it's extremely difficult to parameterize them all. It's easier to test a specific set of barrels all made not to the same manufacturer's specification, but rather, all made in precisely the same way, and note the performance under different rounds, than it is to attempt to parameterize sub-elements of the barrel like:
  • type of barrel steel (although, if specific ratios off the steel phase diagram are known, they might be able to be parameterized, above)
  • the way the barrel was made (cast, forged, hammered, drilled, rolled, cut/lathed)
  • the way the barrel was heat-treated (hardening)

Why? Because it's there. It may also help hand-loaders get the most out of their loads and propellants while remaining on this side of the limits of safety.

On a more practical note, it's sufficient for nearly all practical purposes to use the cartridge manufacturer's specifications with respect to both round performance, and if you're loading your own, use the powder's performance charts to determine how much to use given the caliber and mass of bullet.

Then, there's this outstanding resource.

And this one.

Finally, there's always Grandpa's answer: 'Bout that long... :ROFLMAO:
 

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Or simply as long as it takes...
If you really really like differential equations ... :eek:

I’d start by measuring times (no small trick in itself) and relate to various parameters.

But FIRST check to see if anyone has done this already.

:)
 

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What is a New York second - Alex.
 

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"How long does a bullet spend accelerating in the barrel of a rifle?"

Longer than the time for a liberal to go from calm to violence at the sight of a "MAGA" hat.
 

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The original question, posted here, was: "How long does a bullet spend accelerating in the barrel of a rifle?"

I think it's safe to say the vast majority of people on this forum know that varies significantly, depending upon bullet caliber, bullet mass, cartridge propellant, cartridge primer and primer type, not to mention the length of the barrel, twist of rifling grooves, depth of the rifling grooves, width of the rifling grooves, type of barrel steel, the way the barrel was made (cast, forged, hammered, drilled, rolled, cut/lathed), and the way the barrel was heat-treated (hardening).

Having take a class or three in materials engineering, I do believe this can be reduced to some approximating equations, but some of the coefficients must be placarded. That is, they're discrete elements, which vary in steps between the above mentioned factors, such as the type of powder that was used. I'm not going to begin to dig into my college texts to derive a single equation t=f(x), but let's at least figure out which components can be parameterized and which will require tabular data. Here's my initial stab at it:

Continuous (can be included in the equation using algebraic and/or calculus equations):

bullet caliber
bullet jacket (affects friction)
bullet composition (jacket and composition affect in-barrel deformation, which affects both friction and its ability to seal against propellant gases)
bullet mass
cartridge propellant
length of the barrel
twist of rifling grooves
depth of the rifling grooves
width of the rifling grooves

Discrete (varies widely from one brand to another, and so much be introduced via placard coefficients into the equation):

cartridge propellant
cartridge primer (via make and model)
barrel make and model*

*barrels: So many factors go into making a barrel that it's extremely difficult to parameterize them all. It's easier to test a specific set of barrels all made not to the same manufacturer's specification, but rather, all made in precisely the same way, and note the performance under different rounds, than it is to attempt to parameterize sub-elements of the barrel like:
  • type of barrel steel (although, if specific ratios off the steel phase diagram are known, they might be able to be parameterized, above)
  • the way the barrel was made (cast, forged, hammered, drilled, rolled, cut/lathed)
  • the way the barrel was heat-treated (hardening)

Why? Because it's there. It may also help hand-loaders get the most out of their loads and propellants while remaining on this side of the limits of safety.

On a more practical note, it's sufficient for nearly all practical purposes to use the cartridge manufacturer's specifications with respect to both round performance, and if you're loading your own, use the powder's performance charts to determine how much to use given the caliber and mass of bullet.

Then, there's this outstanding resource.

And this one.

Finally, there's always Grandpa's answer: 'Bout that long... :ROFLMAO:
hillary what difference.jpg
 

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The original question, posted here, was: "How long does a bullet spend accelerating in the barrel of a rifle?"

I think it's safe to say the vast majority of people on this forum know that varies significantly, depending upon bullet caliber, bullet mass, cartridge propellant, cartridge primer and primer type, not to mention the length of the barrel, twist of rifling grooves, depth of the rifling grooves, width of the rifling grooves, type of barrel steel, the way the barrel was made (cast, forged, hammered, drilled, rolled, cut/lathed), and the way the barrel was heat-treated (hardening).

Having take a class or three in materials engineering, I do believe this can be reduced to some approximating equations, but some of the coefficients must be placarded. That is, they're discrete elements, which vary in steps between the above mentioned factors, such as the type of powder that was used. I'm not going to begin to dig into my college texts to derive a single equation t=f(x), but let's at least figure out which components can be parameterized and which will require tabular data. Here's my initial stab at it:

Continuous (can be included in the equation using algebraic and/or calculus equations):

bullet caliber
bullet jacket (affects friction)
bullet composition (jacket and composition affect in-barrel deformation, which affects both friction and its ability to seal against propellant gases)
bullet mass
cartridge propellant
length of the barrel
twist of rifling grooves
depth of the rifling grooves
width of the rifling grooves

Discrete (varies widely from one brand to another, and so much be introduced via placard coefficients into the equation):

cartridge propellant
cartridge primer (via make and model)
barrel make and model*

*barrels: So many factors go into making a barrel that it's extremely difficult to parameterize them all. It's easier to test a specific set of barrels all made not to the same manufacturer's specification, but rather, all made in precisely the same way, and note the performance under different rounds, than it is to attempt to parameterize sub-elements of the barrel like:
  • type of barrel steel (although, if specific ratios off the steel phase diagram are known, they might be able to be parameterized, above)
  • the way the barrel was made (cast, forged, hammered, drilled, rolled, cut/lathed)
  • the way the barrel was heat-treated (hardening)

Why? Because it's there. It may also help hand-loaders get the most out of their loads and propellants while remaining on this side of the limits of safety.

On a more practical note, it's sufficient for nearly all practical purposes to use the cartridge manufacturer's specifications with respect to both round performance, and if you're loading your own, use the powder's performance charts to determine how much to use given the caliber and mass of bullet.

Then, there's this outstanding resource.

And this one.

Finally, there's always Grandpa's answer: 'Bout that long... :ROFLMAO:
Classic case of overthinking.


3300 fps

On his Barrel Tuner page, Varmint Al figured out that the amount of time a bullet spends in a barrel during firing is under . 002 seconds. Al writes: “The approximate time that it takes a 3300 fps muzzle velocity bullet to exit the barrel, assuming a constant acceleration, is 0.0011 seconds.
 

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I had a friend who was an expert in external ballistics. [He is past now]
He also knew a thing or two about internal ballistics [ but not his specialty]
He had an elaborate setup that included a Ransome rest, a servo trigger, and a very high speed camera, to figure out lock time, ignition time and acceleration time. I would imagine you could also time the bullet with that also.
He used this information mostly to rate primers. Which ones were most consistent, Which ones would light magnum powder charges the most efficiently, etc...
High speed cameras have come way down in price over his stuff, So if you were really interested in this , That would be one way to know.
 

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Don't know, don't care.
 
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It's all relative.

Sometimes pretty fast.

.220 Swift. The highest velocity I ever saw measured over the chronograph was fired through this Ruger 77V used a handload having a 10-shot average velocity of 4255 feet per second with a 45 grain Sierra spitzer over a suitable charge of IMR 3031.



Sometimes, not so fast.

.455 Webley. A deliberate handloaded effort to see how low we could go in this Webley Mark IV proved to be "almost, but not quite nearly" fast enough using an unsuitably mild charge of Red Dot under a 185 grain plated truncated cone bullet intended for the .45 ACP. I didn't require the use of the chronograph in this instance, but rather was able to gauge muzzle velocity simply by sight.





 

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Discussion Starter #18

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So for us dumb folks can we just get our chronograph out, find the velocity and divide the barrel length by it to get a close approximation of the time it spends in the barrel?

Seems way easier than doing all that complicated math.

Or we can just say a very, very, very short amount of time and call it good.

I will leave the complicated math to those who really love that stuff.
 
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