What is a "Node"?

[Richard Coody]

Yep.

Are you a mechanical engineer or a PHD physicist?

 

[JLT]

Are you a mechanical engineer or a PHD physicist?

PhD. in Mathematics, Computational Theory, Numerical Mechanics. More than casually familiar with physics.

 

[Richard Coody]

PhD. in Mathematics, Computational Theory, Numerical Mechanics. More than casually familiar with physics.

So you can understand the problem.

You believe with all the different variables involved you can reduce it to an equation that can be solved?

 

[Joe R]

PhD. in Mathematics, Computational Theory, Numerical Mechanics. More than casually familiar with physics.

Awesome ,
I've been praying for someone with an interest in shooting and background in math/physics. We sure can use someone to continue Chris Long's work.

Joe

 

[Richard Coody]

Seems to me if it were true that a mathematical equation could solve this problem then you could take 10 barrels with the same length and.contour from a premium barrel maker and do your calculations and with the same brass, bullet and powder charge they would all shoot the same.

Just doesn't happen that way in the.real world.

 

[Ned Ludd]

Seems to me if it were true that a mathematical equation could solve this problem then you could take 10 barrels with the same length and.contour from a premium barrel maker and do your calculations and with the same brass, bullet and powder charge they would all shoot the same.

Just doesn't happen that way in the.real world.

Sure it can, I've seen it on more than one occasion. I generally order a couple barrels chambered at the same time for my competition rifles. A new barrel often ends up at essentially an identical load as the previous barrel started out. The caveats to that are that the barrels were chambered at the same time, by the same smith, with the same reamer, so they were not only close in external dimensions, but internal as well. Additionally, the same brass and reloading components were used. I'm not claiming it happens every single time, only that it can and does happen more often than is likely to be due solely to chance.

 

[JLT]

So you can understand the problem.

You believe with all the different variables involved you can reduce it to an equation that can be solved?

Any physical system can be modeled. Parameters that are likely to vary from system to system can also be accommodated. By these, I mean things like to what degree a specific bolt face is out of square with the axis of the bore, tenon thread engagement, specific leade and throat geometry, etc. Now, physical measurements would be required for such things, thereby bringing significance and practicality back into the question. Possible? Absolutely. Relatively simple models can get pretty close. Like most things, that last little extra bit of precision comes at a disproportionate cost of time and complexity. Let's just assume that a fully-featured model could be expressed in 2,000 lines of code. I'd guess that 95%, perhaps more, of the correct solution would be delivered with 200 lines of that code base.

As you correctly pointed out in an earlier post, gathering and inputting the data for all of these parameters would be a chore and a half.

 

[Richard Coody]

Sure it can, I've seen it on more than one occasion. I generally order a couple barrels chambered at the same time for my competition rifles. A new barrel often ends up at essentially an identical load as the previous barrel started out. The caveats to that are that the barrels were chambered at the same time, by the same smith, with the same reamer, so they were not only close in external dimensions, but internal as well. Additionally, the same brass and reloading components were used. I'm not claiming it happens every single time, only that it can and does happen more often than is likely to be due solely to chance.

Just one question. Was that powder, charge, bullet and seating depth developed from an equation or typical load development?

 

[Joe R]

Seems to me if it were true that a mathematical equation could solve this problem then you could take 10 barrels with the same length and.contour from a premium barrel maker and do your calculations and with the same brass, bullet and powder charge they would all shoot the same.

Just doesn't happen that way in the.real world.

To expect an exact answer is unrealistic and unreasonable.

Most mathematical models of physical phenomena are approximations, but they can be refined and save lots of time and money in the real world. That's why I use OBT and Quickload. If you don't want to, that's fine, don't. Just stop being so argumentative and take your meds.

 

[JLT]

Awesome ,
I've been praying for someone with an interest in shooting and background in math/physics. We sure can use someone to continue Chris Long's work.

Joe

All I need is a lab for physical testing ... whiteboards and workstations I got.

I did most of my research in DOD-funded labs. Gobs of computing power, great instrumentation and no problems getting resources thrown at physical testing.

BTW, I'm looking forward to enjoying the Better Life in Texas soon.

 

[JLT]

To expect an exact answer is unrealistic and unreasonable.

Most mathematical models of physical phenomena are approximations, but they can be refined and save lots of time and money in the real world. That's why I use OBT and Quickload. If you don't want to, that's fine, don't. Just stop being so argumentative and take your meds.

And to expand on that observation, an exact answer might very well be indistinguishable in practical terms from a well thought out approximation. Such an approximation can provide a very accurate barrel position at bullet exit (down to a gnat's eyelash - scientific term), but atmospherics introduce all sorts of stuff from that point on.

 

[savagedasher]

I have 5 dashers all shooting the same powder and amount same bullet same case capacity . Barrels are 28" to 31"
Barrel time is 1. 312 to 1.231 which is the correct number I should use All 5 shoot .250 or less I just would like to know what number is correct.
Is it a theary or a fact . Larry

 

[Richard Coody]

I have 5 dashers all shooting the same powder and amount same bullet same case capacity . Barrels are 28" to 31"
Barrel time is 1. 312 to 1.231 which is the correct number I should use All 5 shoot .250 or less I just would like to know what number is correct.
Is it a theary or a fact . Larry

That is a.fact!

I am bowing out of this discussion

Don't mean to be so argumentative.

I am just old school.

 

[savagedasher]

That is a.fact!

I thought so so it doesn't matter . When I change powder types the numbers mean nothing . Larry

 

[Ned Ludd]

Just one question. Was that powder, charge, bullet and seating depth developed from an equation or typical load development?

The answer is actually both. What I have found with successive barrels that are the same length, contour, twist rate, chambering, etc., is that even if you are using totally different component Lot #s of everything by the time you screw the new barrel on, they still often end up very close to one another in terms of barrel occupancy time. Whatever combination of the same type, but different Lot #s of powder, primers, brass bullets, etc. is required to produce the same barrel time will be very close in terms of performance to the previous barrel. Barrel occupancy time is predictable to a fair degree of precision.

One example of this general phenomenon is the use of Berger 200 Hybrid and/or 200.20X bullets in F-TR. The vast majority of users with ~30"-31" barrels are hitting a "node" that falls somewhere in the 2640-2680 fps range with either Varget or H4895. Without a doubt there are subtle differences between their rifles such as freebore, or perhaps twist rate, or even in the brass they are using. However, they all come up with final loads that are very close in terms of velocity, or more importantly, barrel time. In fact, I'm surprised that they end up as close as they are given the slight differences in setups. Nonetheless, there appears to be an accuracy "node", if you want to call it that, that falls within this fairly narrow (in terms of percentage) velocity window for barrels of a given length. Literally hundreds, if not even thousands, of F-TR shooters have tuned 200 gr loads to this window. That is more than chance. I can't tell you with any certainty whether that is the result of harmonics, longitudinal shockwaves, or any other possible explanation. What I can say is that it is reproducible and to a reasonable degree, predictable.

 

[savagedasher]

That is a.fact!

I am bowing out of this discussion

Don't mean to be so argumentative.

I am just old school.

I'm very old school To me the numbers don't mean anything .
The only answer I count on is the holes in the paper . Larry

 

[gunsandgunsmithing]

Tuners are very simple to use. Explaining how they do what they do..if anyone knows it all, is not.
But..I can tune my rifle with a tuner in much less time than it took me to read this thread.
That said, there is good info here. Keep it going.
---Mike Ezell

p.s.--- very small tuner adjustments do make a huge difference. This is not theory.

 

[Steve Blair]

Any physical system can be modeled. Parameters that are likely to vary from system to system can also be accommodated. By these, I mean things like to what degree a specific bolt face is out of square with the axis of the bore, tenon thread engagement, specific leade and throat geometry, etc. Now, physical measurements would be required for such things, thereby bringing significance and practicality back into the question. Possible? Absolutely. Relatively simple models can get pretty close. Like most things, that last little extra bit of precision comes at a disproportionate cost of time and complexity. Let's just assume that a fully-featured model could be expressed in 2,000 lines of code. I'd guess that 95%, perhaps more, of the correct solution would be delivered with 200 lines of that code base.

As you correctly pointed out in an earlier post, gathering and inputting the data for all of these parameters would be a chore and a half.

I worked on the Ultra Lightweight Howitzer program with Picatinny Arsenal as the program lead. Other participants included General Atomics, Watervliet Arsenal, Benet Labs and Army Ballistics Research Lab (BRL).

The time, money, personnel and resources devoted to artillery, terrestrial and naval, dwarf that accorded small arms. The scientists at BRL and Benet characterized internal ballistics from empirical data because they believed it too complex to reliably model from first principles. They had no practical computational resource restraints. If the problem could have been modeled to the precision you suggest in 2000 LOC, they certainly would have done it.

They also had little trouble gathering empirical impulse, barrel excursion and dynamics data. An instrumented M198 was taken to Aberdeen and fired. Modeling systems is fine, I use computational models almost every day. But there are times when it just makes more sense to run experiments and observe results.

 

[Bart B.]

Seems to me if it were true that a mathematical equation could solve this problem then you could take 10 barrels with the same length and.contour from a premium barrel maker and do your calculations and with the same brass, bullet and powder charge they would all shoot the same.

All of my dozen or so match rifle barrels were Hart, 1:11" twist, 6-groove, .2990" bore, .3077" groove, 26" long, 1.200" to .900" straight taper, 11 deg. face. Same respective loads for 168, 180, 185, 190, 197 and 200 gr. bulletsj tested as good as could be had.

No calculations as barrel time's difficult to measure exactly. Just used the popular loads others did with similar barrels.

 

[Bart B.]

What I have found with successive barrels that are the same length, contour, twist rate, chambering, etc., is that even if you are using totally different component Lot #s of everything by the time you screw the new barrel on, they still often end up very close to one another in terms of barrel occupancy time. Whatever combination of the same type, but different Lot #s of powder, primers, brass bullets, etc. is required to produce the same barrel time will be very close in terms of performance to the previous barrel. Barrel occupancy time is predictable to a fair degree of precision.

Which explains why Sierra doesn't work up loads for each lot of components. Same recipie for each bullet. Their best match bullets shoot 10-shot groups well under half MOA at 200 yards, consistently.