Caliber Thought Experiment.

[BitchinCamaro]

Please move if this belongs somewhere else, but I figured PRS is currently the hotbed of caliber discussion so I posted it here.

Take 2 cartridges of the same caliber (for example, .308 and .30-06). Then make 2 absolutely identical barrel blanks with relatively infinite diameters and perfect internal metallurgical properties. Think big, like a 20 mile diameter barrel. Also, these barrels have literally laser straight bores and rifling that maintains twist and land/groove dimensions with electron-scale resolution.

Each perfect barrel is chambered perfectly cocentric to their respective cartridge, with the jump to lands being identical for both. The bullets are perfectly identical in mass and dimension down to the atom. Primer charge compound is measured to the molecule and ignited by induction...perfectly. You get the point.

Now, assuming that these perfect bullets are fired at identical velocities in perfectly identical conditions in space and time, at what distance would there be enough difference (qualified broadly) in groupings to discern between cartridges?

Edited December 10, 2015 by BitchinCamaro

[Hi-Power Jack]

perfect bullets are fired at identical velocities in perfectly identical conditions , at what distance would there be enough difference in groupings to discern between cartridges?

Sounds to me like there would be NO difference.

Perfect, and identical, should be the same.

[427Cobra]

A 30 cal pill of the same weight, going the same speed, who knows which would be more accurate, but I do know if you show up at a PRS match shooting a 30 cal, someone shooting a 6 or 6.5 cartridge from a short action is gonna spank your ...!

[Rasyad]

I am curious as well. What are the factors that control long distance bullet stability? I know knothing about such things but read somewhere that bullets vary at how well they handle the deceleration from supersonic speed. Is this a clue?

Rasyad

[38superman]

The answer is simple. In your theoretical scenario, everything is equal. The only difference is cartridge. That difference is inconsequential if the bullets leave the barrel with the same rotational and linear velocities. The only thing that affects the bullet after exiting the barrel are environmental factors. Again you have made then identical as well. Your answer is that if all things are equal in the absolute, the results will be equal. Physical law doesn't change from one shot to another. Point of impact will not vary at any range.

Edited December 10, 2015 by 38superman

[BitchinCamaro]

In your theoretical scenario, everything is equal. The only difference is caliber.

Calibers are the same. Cartridge is different. Edit: I think we caught that at the exact same time.

The same conditions can be applied to any 2 cartridges of the same caliber loaded to equal muzzle velocity. Let's say it's 6.5 Creedmoor and 6.5x47 Lapua.

.308 and .30-06 are ideal because there has already been whole generations worth of debate and conjecture over the merits of one over the other.

There's so much guntalk about the "inherent accuracy" of particular cartridges lately. For personal clarification I'm just wondering how variables other than velocity can contribute to trajectory (all other considerations being ideally equal) , namely chamber dimensions.

Once that's established, then the infinitely perfect parameters can begin to be peeled away to begin to consider introduced disparities like barrel harmonics and dwell times. But for the sake of this thread, I still wanted to maintain impossibly perfect conditions to see if I'm missing something.

it's a long winded way of asking "is this a stupid question?"

Edited December 11, 2015 by BitchinCamaro

[Blacksamwell]

When chamber differences result in velocity differences at the muzzle then you'll begin seeing differences at the target.

However, in the thought experiment proposed, identical bullets leave identical bores at identical speeds. In this scenario, any influence of different chambers has been eliminated through the parameters of the thought experiment.

Right?

[Hi-Power Jack]

assuming perfect bullets are fired at identical velocities in perfectly identical conditions in space and time, at what distance would there be enough difference (qualified broadly) in groupings to discern between cartridges?

You posted this question at 4:30 a.m.

Now that the sun is up, do you STILL feel this is a GREAT question?

[warpspeed]

Velocity is only part of the equation. The acceleration of the projectile is the other part.

So are you are saying that the 2 bullets are being accelerated at the same rate and to the same velocity ?

[P.E. Kelley]

In your scenario the first shot of each would be the same...to shoot groups...velocity between shots must be as close to the same (low SD)

The loading density of the 06 would likely be less than the 308 for the same velocity. And loading density has an influence on getting low SD's

[BitchinCamaro]

You posted this question at 4:30 a.m.

Now that the sun is up, do you STILL feel this is a GREAT question?

First, I'm in a different time zone.

Second, like...Dude. Sticks are like tree bones .

Velocity is only part of the equation. The acceleration of the projectile is the other part.

So are you are saying that the 2 bullets are being accelerated at the same rate and to the same velocity ?

Leaving out identical acceleration was intentional. I didn't want to tip my hand, but this is fundamentally what I was getting at. I was poking through some of my old Physics textbooks and was just wondering under what circumstances a projectile deviates from the standard equation set for uniformly accelerated (Non Hamiltonian) motion, and where the window was for introducing deviations from expected trajectories.

Load density was another consideration, Mr. Kelley, for both reasons of dwell time at the chamber end and perhaps any resulting turbulance at the other end. Deformation of the bullet as the bullet entered the rifling was also a consideration.

To clarify, this question isn't necessarily about absolute accuracy or long range stability (though both are corollary). It's just an attempt to discern any inherent differences between cartridges punting the same caliber bullet.

Edited December 12, 2015 by BitchinCamaro

[Wild Gene]

Warpspeed asked my question. If that wasn't a huge part of the equation, along with load density, then powder burn rate would not have such a huge effect on the accuracy of one .30 caliber round vs another .30 cal round, and we have all been wasting a lot of time.

wg

[wgj3]

I love that the our shooting community has the capacity and desire to ask things like this and is able to discuss it without sounding silly.

[dauntedfuture]

So i think the question might be a little sillt too but.... what i think you are going to find is that one of the cartridges will produce lower ES and SD numbers. This will more LIKELY be the shorter fatter powder colum. What i think you will really find is that one barrel will last longer then the other, the cartridge where more of the powder burns inside of the case will erode less of the throat and "last longer"