Beantown: Separate Question On Pressures
I didn't want to use up the alloted responses by asking an 'off topic' question in ECC's string about the Taurus Judge. So, My question below:
Bean, when you are talking pressure, are you talking total pressure exerted in the chamber, or pressure per in/sq? Total pressure exerted means you will have to factor in the amount of square inches the PSI is working against.
Consider the .22 Hornet. Much higher PSI than a .375 H&H. But the H&H has more total pressure exerted, due to the square inches in the chamber being considerably greater.
Is there an 'end formula' to take the PSI of sumsuch caliber, and factor in the chamber's square inches to come up with a workable force? Thanks, Joe
Bean, when you are talking pressure, are you talking total pressure exerted in the chamber, or pressure per in/sq? Total pressure exerted means you will have to factor in the amount of square inches the PSI is working against.
Consider the .22 Hornet. Much higher PSI than a .375 H&H. But the H&H has more total pressure exerted, due to the square inches in the chamber being considerably greater.
Is there an 'end formula' to take the PSI of sumsuch caliber, and factor in the chamber's square inches to come up with a workable force? Thanks, Joe
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I don't really consider myself an expert in this area, but I was simply referring to max chamber pressure, which is what SAAMI uses. Its generally given in pounds per square inch (PSI).
Given two rounds that fire the same bullet at the same velocity, the one with the larger chamber ought to be operating at a lower max pressure.
If I understand the physics correctly here, pressure will (ie MUST) distribute itself evenly throughout the chamber, including on the bullet base.
So the max pressure on the base of the bullet has to be the same as the max chamber pressure.
The pressure exerted against the chamber wall doesn't do anything (or at least you HOPE it doesn't. . .you really do NOT want the chamber wall going anywhere!).
If you want to determine the maximum FORCE applied to the bullet, what you do is take the maximum actual pressure (in pounds per square inch), then multiply that by the surface area of the bullets base (which per elementary geometry will equal Pi x (half the bullet caliber)^2 ).
This will yield a figure in pounds, equal to the amount of force exerted on the bullets base during maximum chamber pressure.
Note that this figure, all by itself is of limited value.
Max pressure only lasts for an instant, and its preceded and followed by lower pressures over time.
How fast the bullet is going to go is going to depend on the total amount of force exerted on the bullet over the time its in the barrel. That's a complicated metric involving obtaining the area of the curve of pressure vs. time.
EDIT:
quote:Consider the .22 Hornet. Much higher PSI than a .375 H&H. But the H&H has more total pressure exerted, due to the square inches in the chamber being considerably greater.
This is true, but it doesn't tell you a lot about how fast the bullet is going to be moving, and presumably that's what you care about!0 -
Thanks, Bean! You are a good man in the clutch! (Or hydramatic)[^] 0 -
comparing a .375" dia projectile, to a .224" projectile is apples to oranges. You must compare "like" diameter projectiles to have a good comparison. Now, the pressure comparison will depend on case capacity, amount of propellant, and burn rate of each propellant.
i.e. I can run a 223rem to a much higher pressure than a 220swift,....IF I run a small load of slow podwer behind a 50gr pill in the swift, and a large charge of fast buring powder in the 223 with the same 50gr projectile, I get higher chamber pressures in the 223 than the swift. Now,..loaded to normal max pressures with appropriate powders for each, the chamber pressure will come in close to the same for each. However, the larger amount of powder in the swift, will make for a longer burn time due to more powder, which will accelerate the swift bullet to a higher MV than the 223.
The variables you are asking about are many.
Also, the larger bore dia, will accept more powder, behind a heavier bullet, but still end up at similar pressures. Reason being, the larger exit dia of the 375 case and bore, will allow escape of gasses more readily than the smaller .224 dia bore.
As a side note, pressure curves are different with each powder burn rate (assuming like bore dia and bullet weight) in any given chambering. Fast powders acheive max pressure faster, but also show a reduction in pressure faster, whereas, slower powders, acheive max pressure slower, but the lessening of pressure takes longer as the remaining propellant is still being burned. This is why slow powders are better for heavier bullets,..they continue the accleration during "dwell time" as the the bulet is still in the bore whereas the faster powder reaches its pressure faster, but is consumed faster, and has less remaining propellant to brun during "dwell time". Therefore, the lighter bullet with a faster powder is acclerated in less time, and allowed to exit, while the heavier bullet is acclerated slower, but for more time while in the bore. This equates to the heavy bullet gaining speed over a longer time period.0 -
All good points.
To recap, the original thread was about the wisdom of shooting .45ACP from moon clips in a Taurus Judge .45LC revolver. I pointed out that .45ACP runs at much higher operating pressures than either .410 shotshells or .45LC, and that this, coupled with the less than excellent reputation of Taurus wheelguns, is a good reason to tread cautiously.
ECC asked why pressures are so much higher in the .45ACP (21,000 PSI vs 14,000), even though the .45LC can fire similar weight and caliber bullets faster.
So the original question actually was an "apples to apples" comparison. You can see my response there.
The quick answer relates to the two different platforms the rounds were designed for.
Again, conventional semi-auto pistols HAVE to generate certain pressure levels just to reliably cycle their actions. Revolvers don't have that constraint.
Conversely, the biggest practical constraint on 45LC load pressures is its historical legacy as a 19th century black powder round. Even though today the round *could* be loaded to much higher pressures using modern smokeless powders (eg that's effectively what the .454 Casull and .460 SW magnum rounds are) in practice loads that hot would detonate older guns not designed to handle modern magnum pressures.
Getting into the physics, apart from different types of loads tailored to meet the design specs referred to above, at least part of the difference between the two in max pressure is simple volume.
Because of Boyle's law (for a given quantity of gas, pressure x volume will equal a constant), if you take two otherwise identical loads with similar powder charges and bullets, the one fired from the larger chamber will achieve a lower peak pressure because the propellant gas has a greater volume to expand in.0 -
Thanks, fellas, for taking the time with me. Best again, Joe 0 -
ahhh, I now see this is about the "judge" threads which deteriorated via the urinary olympics.
I wonder why they don't make newer guns in say the 45lc, and specify a different designation of ammunition so as not to have someone destroy an older pistol made for the low pressures of the old black powder loads. But then again, someone would no doubt try the new ammunition in an old gun, and probably win some frivelous lawsuit.0 -
CorBon has been producing 3 different higher pressure .45 Colt rounds for a few years now. They call them .45 Colt "magnum" and these rounds will equal or better standard .44 Magnum loadings. They also specify the firearms for which they are suitable, generally single shot rifle/pistol (e.g. TC), Ruger Blackhawk and "old model" Vaqueros, Freedom Arms revolvers and a couple lever action big bores with heavy duty actions (e.g. Marlin Model 1894) - generally any firearm that is also produced in .44 Magnum or higher pressure chamberings.
Good reading on this topic here: http://www.chuckhawks.com/high-pressure45.htm0 -
quote:Originally posted by JustC
I wonder why they don't make newer guns in say the 45lc, and specify a different designation of ammunition so as not to have someone destroy an older pistol made for the low pressures of the old black powder loads. But then again, someone would no doubt try the new ammunition in an old gun, and probably win some frivelous lawsuit.
Just answered your own question!
I think in fact most of the new-manufacture guns in 45LC can safely handle pressures much higher than the relatively low 45LC spec. I'd actually be a bit surprised if the "Judge" didn't fall into this category. But why would gun makers give reloaders a license to blow themselves up and then sue the gunmakers by advertising this fact?
Its not just the gun, but ordinary 45LC brass is really not designed to operate at modern magnum pressures. I think the special high pressure .45LC rounds use thicker brass.
If you want a high pressure .45LC, its been around for 50+ years as the .454 Casull magnum.
I think a practical reason why super heavy .45LC loads aren't prevalent is just because with their .45ACP-like (or even slightly greater) ballistics, they do what they need to do for defense without further beefing them up.
If it ain't "broke", why fix it?0
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