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A question for the experts #6368328 07/13/16 11:20 PM
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Texas Dan Online Content OP
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What causes a given rifle to shoot better and produce tighter groups with certain brands and/or loads of ammo?


"Some people will never like you because your spirit irritates their demons."
Re: A question for the experts [Re: Texas Dan] #6368373 07/14/16 12:08 AM
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Harmonic balance. Thats why hand loading works so well. You can tune the balance.


This explains it better than I could. https://www.shootingsoftware.com/barrel.htm



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Re: A question for the experts [Re: Texas Dan] #6368405 07/14/16 12:34 AM
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^^^^ plus little fellows known as gremlins that attack barrels and bullets and powders and burning rates even to the point of how much the ammo has been transported. And don't forget good lady Mother Nature with temps and humidity and pressure of her own.


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Re: A question for the experts [Re: Texas Dan] #6368427 07/14/16 01:00 AM
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The Science of Ammunition- where do you start!!?? There's lots to discuss. Ask a more detail question, instead of such a broad range, and I'll help. In a nut shell, it boils down to the right powder and powder charge for the right bullet and caliber used.

I find it interesting when I hear a shooter say "my rifle doesn't like that bullet". Most of the time, the rifle doesn't like the load (i.e.- the powder and powder charge used) with that bullet. I have taken MANY rifles and dialed in a very accurate load with my custom ammo on a rifle with the same bullet that didn't shoot well in factory ammunition. The customer is usually surprised when I get it to shoot.



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Re: A question for the experts [Re: Texas Dan] #6368461 07/14/16 01:44 AM
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I don't doubt that, but sometimes you DO find that a rifle really just does NOT like a particular bullet---for whatever reason.


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Re: A question for the experts [Re: Texas Dan] #6368462 07/14/16 01:45 AM
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Do rifle manufacturers take such things into account when designing gun barrels? It would seem necessary to tout their "out of the box" accuracy.


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Re: A question for the experts [Re: Texas Dan] #6368466 07/14/16 01:54 AM
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Other than rate-of-twist and the way the freebore is cut, generally NO. Ammo is designed to function well (hopefully) in guns the way they are made, not the other way around.


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Re: A question for the experts [Re: Michael W.] #6368539 07/14/16 03:10 AM
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Originally Posted by Michael W.


Harmonic balance. Thats why hand loading works so well. You can tune the balance.


This explains it better than I could. https://www.shootingsoftware.com/barrel.htm

And...



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Re: A question for the experts [Re: Texas Dan] #6368901 07/14/16 03:24 PM
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shortest answer I can give:

The end of your barrel moves up and down in something that approximates a Sine curve during firing:



you want the bullet to exist the barrel at a peak so that you're not inducing an additional force vector on the bullet, not on the way up or down. You get to that peak by tweaking the amount of powder and the COAL (jump/jam) of the loaded round.

Re: A question for the experts [Re: Texas Dan] #6369069 07/14/16 05:22 PM
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Something I find interesting is using Quick load to come up with a better load. I mistakenly thought that the load that was most efficient would be the most accurate. Such is just not the case. Some of my best shooting loads are in the 85-89% range. I know I should have known better...it can only predict based on the numbers.


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Re: A question for the experts [Re: bside] #6369427 07/14/16 10:22 PM
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Originally Posted By: bside
shortest answer I can give:

The end of your barrel moves up and down in something that approximates a Sine curve during firing:



you want the bullet to exist the barrel at a peak so that you're not inducing an additional force vector on the bullet, not on the way up or down. You get to that peak by tweaking the amount of powder and the COAL (jump/jam) of the loaded round.


Your explanation has me a liitle confused. Would not the points at which the waveform crosses the zero axis be the point where you want the bullet to exit the barrel. Whatever the case, the diagram explains how barrel length and makeup, as well as other factors that impact bullet velocity (powder charge, bullet weight, rifling twist, and even the burn rate of the powder) all play a role.

Still, the most accurate rifle in the world, from a design perspective, is no more accurate than the capabilities of the one pulling the trigger. It's a fact wasted on those who somehow believe that even though they seldom practice, they are as accurate as their rifle.


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Re: A question for the experts [Re: Texas Dan] #6369457 07/14/16 11:03 PM
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Dan, you want the bullet to exit when the speed of motion is at a minimum, which is at the maximum and minimum values of deflection. Where you cross the x-axis, the speed of motion is maximum.

In fact, some say that you want the bullet to exit the muzzle as it is approaching the very top of the peak. The theory is that if your lowest velocity round (taking shot-to-shot variations into account) exits just as the muzzle reaches the top of its vibration pattern, then the other shots which are higher velocity will exit a tad bit sooner BEFORE the muzzle is at its zenith. This helps compensate for the minute differences in trajectory due to velocity differences. Benchresters have told me that when the rifle is tuned properly this results in minimal vertical spread at a particular range---but ONLY at that range. If the rifle's tuned up for 100 yards, then it won't shoot well at 200.


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Re: A question for the experts [Re: RiverRider] #6369633 07/15/16 01:15 AM
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Originally Posted By: RiverRider
Dan, you want the bullet to exit when the speed of motion is at a minimum, which is at the maximum and minimum values of deflection. Where you cross the x-axis, the speed of motion is maximum.

In fact, some say that you want the bullet to exit the muzzle as it is approaching the very top of the peak. The theory is that if your lowest velocity round (taking shot-to-shot variations into account) exits just as the muzzle reaches the top of its vibration pattern, then the other shots which are higher velocity will exit a tad bit sooner BEFORE the muzzle is at its zenith. This helps compensate for the minute differences in trajectory due to velocity differences. Benchresters have told me that when the rifle is tuned properly this results in minimal vertical spread at a particular range---but ONLY at that range. If the rifle's tuned up for 100 yards, then it won't shoot well at 200.


Thanks. This makes complete sense. In lay terms, you want the bullet to exit the barrel end when it is "still", which occurs at the peaks of the shockwaves that bounce back and forth along the barrel axis. This would produce a specific ballastic performance, meaning the rifle and scope could be set to the zeroing preferred by the shooter with that round.

It would be a matter of trial and error to determine what round will perform in this way with a given rifle.

Last edited by Texas Dan; 07/15/16 01:22 AM.

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Re: A question for the experts [Re: blackcoal] #6369652 07/15/16 01:36 AM
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Originally Posted By: blackcoal
^^^^ plus little fellows known as gremlins that attack barrels and bullets and powders and burning rates even to the point of how much the ammo has been transported. And don't forget good lady Mother Nature with temps and humidity and pressure of her own.


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Re: A question for the experts [Re: Texas Dan] #6369701 07/15/16 02:21 AM
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Originally Posted By: Texas Dan
Originally Posted By: bside
shortest answer I can give:

The end of your barrel moves up and down in something that approximates a Sine curve during firing:



you want the bullet to exist the barrel at a peak so that you're not inducing an additional force vector on the bullet, not on the way up or down. You get to that peak by tweaking the amount of powder and the COAL (jump/jam) of the loaded round.


Your explanation has me a liitle confused. Would not the points at which the waveform crosses the zero axis be the point where you want the bullet to exit the barrel. Whatever the case, the diagram explains how barrel length and makeup, as well as other factors that impact bullet velocity (powder charge, bullet weight, rifling twist, and even the burn rate of the powder) all play a role.

Still, the most accurate rifle in the world, from a design perspective, is no more accurate than the capabilities of the one pulling the trigger. It's a fact wasted on those who somehow believe that even though they seldom practice, they are as accurate as their rifle.


No, because the barrel *is moving* up/down at those points, you want a point at which it's not moving/moving as little as possible. Think of flicking a spinning top inducing wobble and causing the top to fall over earlier -- that's the type of force we're trying to avoid.

look at any slice of time on the graph, you want the least vertical dispersion possible for a given time (plus/minus a small window of each side)

Last edited by bside; 07/15/16 02:22 AM.
Re: A question for the experts [Re: Texas Dan] #6371821 07/17/16 04:26 AM
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To add to what everyone else has said about harmonics, and touch on Texas Dan's question about manufacturing. Every piece of steel is different in the way it will act. Chemical composition and stress from manufacturing, along with other factors will affect the way a barrel behaves. Two identical rifles, rolling off the assembly line one after the other will exhibit different characteristics in relation to load development or ammunition preference. Each has its own personality. They may like the exact same load, or be on opposite ends of the spectrum.

Re: A question for the experts [Re: Texas Dan] #6375386 07/20/16 02:49 AM
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All good information and posts.

I'm sure many others besides myself learned something.


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Re: A question for the experts [Re: RiverRider] #6375515 07/20/16 04:51 AM
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Originally Posted By: RiverRider
Other than rate-of-twist and the way the freebore is cut, generally NO. Ammo is designed to function well (hopefully) in guns the way they are made, not the other way around.

Just to add to the comment - you have to use correct ammo. And here is know-how.
http://www.shilen.com/calibersAndTwists.html

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