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Discussion Starter · #1 ·
Greetings y'all! This may not be the most correct place for this question but you guys seem to be the math and science department 'round here and I've got a question about cartridges. The owners manual for my Tracker 44mag states (according to a post I found here, original in box defective, pg 8 & 9 duplicate) max load is [email protected] 1350fps. What does this mean in relation to force applied to the gun? Seems I'm missing a number to calculate what max is, in regarde to lighter rounds, 180gr 1550fps, or various other combinations. I am aware of the limitations of this lighter firearm frame and do not want to damage or overload my investment. Is it muzzle energy? I searched the last 30+ pages in revolver, factory ammo and here in reloads and have found nothing substantial enough to confirm or negate my suspicions. My copy of the ABC's of reloading is in the mail but I just can't wait to crack this nut. Thank you.

240gr @ 1350fps = Z
180gr @ 1550fps =?
>Z=$bomb
please help me solve for Z
 

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I'll take a shot at this. My suspicion is that you are looking in the wrong direction there, and need to be looking at chamber pressures rather than muzzle energy.

When the cartridge is fired, the powder inside is rapidly burned, increasing pressure in the firing chamber (and barrel, behind the bullet). The bullet, being the weakest link, is pushed down the barrel until either it exits (releasing the remaining gases) or is stopped (for example, a squib load). I remember seeing that, for example, the maximum pressure for a .40 S&W cartridge is 35,000 PSI.

(Now, I begin to make assumptions, so please correct me, anyone, if I make any incorrectly.) Since you know the velocity exiting the barrel, you can compute the acceleration of the bullet. Since force is mass times acceleration, knowing the bullet mass you can compute the amount of force applied to the bullet. Also, knowing surface area of the rear of the bullet, you can then compute the pressure, which would be the force divided by the area. Correct?

My thought experiment to see if I am on the right track. A 4" .40 S&W, using a Hornady 155gr bullet and 5.7gr of Titegroup powder is a maximum load (according to one resource I had available), with a muzzle velocity of 1100 fps. A maximum load for the .40 S&W is 35,000 PSI.

Back of the envelope calculations:
35000PSI = 2.413e8Pa (maximum chamber pressure).
1100fps = 335.3m/s.
4" = 0.1016m.
0.347" = 0.0088m (bullet diameter).
155gr = 10.044e-3kg (bullet mass).
Acceleration (v^2 = v(0)^2 + 2*a*d) is thus 743.8m/s^2.
Force (F=m*a) is then 7470N.
Area (bullet base, pi*r^2) is 6.101e-5m^2.
Pressure (P=F/A) is therefore 1.22e8Pa, which is below the maximum stated above (2.4e8Pa).

Anyone? Hope this helps....
 

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That's better math than I could produce; but while we have the bullet's diameter, would the barrel's exact diameter, as well as the depth of both lands and grooves, determining resistance, affect the calculation?
 

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Yes, the method I did was off the top of my head, and did not take into account the rifling of the barrel, friction, or anything else not mentioned. There may be (and probably is) a better approach-that was just what I could imagine to get a (really) rough approximation. Honestly, as someone who is just starting to look at reloading themselves, my gut feeling would be to look for data with the components to be used, or to contact the component manufacturer(s), and not to trust my safety (or anyone around me) to a set of back-of-the-envelope calculations for this.
 
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I would think there is one more variable - the burn rate of the powder. You could achieve the same muzzle velocity for a given bullet with a fast burning powder - producing most of the velocity early in the bullets travel down the barrel, & probably developing higher peak chamber pressure, OR using a slower burning powder, more gradual acceleration, and probably lower pressure for the same bullet weight.
That is why slower burning powders tend to be recommended for higher weight bullets, and that extra variable makes calculating chamber pressure with muzzle velocity and bullet size & weight something that is beyond my math capabilities.
 

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Discussion Starter · #6 ·
Max chamber pressure, I think that is the third variable my primitive brain is searching for, thank you very much for taking the time to help me with my question. I'm probably going to need a bigger calculator to do all the math mentioned here but it'll give me something to do when insomnia hits. Thanks again
 
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I think there is software out there called Quick Load, or something like that, that calculates approximate pressure for you. I know at least one member here has it, name slips my mind right now.
 

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Max chamber pressure, I think that is the third variable my primitive brain is searching for, thank you very much for taking the time to help me with my question. I'm probably going to need a bigger calculator to do all the math mentioned here but it'll give me something to do when insomnia hits. Thanks again
That's when I do my best thinking and tinkering is late at night haha.
 

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well the member is Ranch Dog!
but lets understand first off and I am not at all familair with the Taurus weapon that you speak, but from a logical position consider this.
First the 44 magnum is not offered in a plus p or higher chamber pressure ammunition, so all 44 magnum facory ammunition should be within safe pressures as per SAAMI.
so logically any factory loaded ammunition should be safe for use.
now recoil, muzzle flash, etc my be different but they should all be under SAAMi standards for chamber pressure in the 44 magnum.
Now if speaking from a reloading standpoint, well then refer to any number of published manuals, manufactures data, etc for safe laoding with various components.
Now as to become clinical lets realize that chamber pressures are derived from an exact weapon/testing apparatus, on a certain day,at a certain temperature, and humidty at a certain altitude, in other words lot of variables, so a certain safety margin is built in, also most modern firearms are tested at a certain over charge, simply because people screw up sometimes!
to much screw up and things come apart however!
but again in factory ammo you should be safe.
powder burn rate, barrel length, actual chamber/cylinder dimensions, actual brass case capacity, over all length of the cartridge, material that the projectile is made of, condition of the bore, all this makes a difference, so if you are trying to figure an exact calculations for all weapons of a certain caliber--well 'Rots of Ruck" on that.
hope this has helped with the confusion.
By the way SAAMI chamber pressures for the 44 Magnums 36,000 PSI.
Welcome to the forum and enjoy your stay.
 

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Over the years there have been both heavy handloads and custom factory loads for the 44 mag and some other calibers. Some like 45 colt loads are listed as Ruger only etc. Garrett loads some custom ammo that is rough on both the shooter and game, their loads are not something I would shoot in mt Tracker 44 mag. I don't feed it a diet of large quantities of heavy bullet hot loads. Over the years I have shot enough of them to tell you for a fact you can shoot a model 29 Smith loose with loads a Ruger Red or Black hawk can eat thousands of. The Taurus recommendations leave something to be desired but bottom line stay 240 grain bullets or less and don't push max loads. Heavy bullets hammer actions when loaded hot. Shoot bunches of them when you are young and your hands will let you know about as the weather changes when you get old. Funny thing about getting old.
 

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Discussion Starter · #11 ·
Sirs, thanks for your input and wisdom, very much appreciated. I have no desire to blow up my gun and wanted to know the limit just so I could stay below it, no need to spend life racing through red lights when I can cruise through yellows.
 
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