How important is one kernel of powder?

[adamjmac]

This is how the math works out.

Suppose your SD is 5.0

For 30 cal if you add +/- 1 kernel of randomness to your loading process that's +/- 1 fps random error which is an SD of 0.5 fps.

That will change your SD to be:
square root ( 5 x 5 + 0.5 x 0.5 ) = 5.025 fps

At 1000 yards 1 fps = 0.03 moa of elevation

Expected 20 shot extreme spread is 4 times the SD.

So the velocity component of your group size has gone from 0.6 to 0.603

The non-velocity component of your group is say 0.3 moa on a good day.

So the final group size will be
sqrt (0.3 x 0.3 + 0.6 x 0.6) = 0.6708 moa without the 1 kernel error
sqrt (0.3 x 0.3 + 0.603 x 0.603) = 0.6735 moa with the 1 kernel error

It will increase your group size by 0.4 %.

 

[Alex Wheeler]

Barrel harmonics can cause small things like .1gn to show up big on target or they can take big things like high es and cancel them out on target. The math just does not predict this.

 

[adamjmac]

Barrel harmonics can cause small things like .1gn to show up big on target or they can take big things like high es and cancel them out on target. The math just does not predict this.

Barrel harmonics is a whole other kettle of fish. The speed of sound in steel means between peaks there is about a 200 fps spread with a 30 inch barrel so you are unlikely to see any effect of harmonics with an F-Class sort of scenario where we keep velocities within a very tight 20 fps range. Every shot is going to be in basically the exact same point on that curve, and if it were not you would see it at close range so it's accounted for within my 0.3 number.

 

[Alex Wheeler]

You can not calculate this stuff with math. Sometimes .1 will not change a group shape or poi at 1k, sometimes it will make a large change. Sometimes it correlates to velocity, sometimes it doesnt. I dont think your giving barrel harmonics enough credit for the effect they can have. You certainly can see the effect of them in a 20 fps window. If your basing all of this on short range groups then your going to have a hard time seeing this.


To answer the OP, it depends on what your shooting. If your not competing, no you dont need to weight to the kernel.

 

[adamjmac]

I believe that looking at effects in detail, understanding how they work and applying math to make sense of it, is an eye opening exercise that cuts through a lot of confusion and complication that doesn't really need to be there.

Otherwise we fall into the trap of mixing all of these concepts together, not taking the time to think about which ones are important and which ones are not, and why, and just getting overwhelmed by a variety of conflicting experiences and opinions that doesn't really lead to any progress.

 

[garandman]

How much does one kernel of powder matter?

Put down your science textbooks and calculators, Hit the reloading bench and then the target range, Pull the trigger and read your chrony and your target.

What's true in your gun may not be true anywhere else ever. And It's only what happens on your target that matters… to you anyway.

 

[BoydAllen]

For those that got sidetracked on the whole equal energy thing, let me remind you that the OP's question was entirely about effect, does it matter in terms of what happens at the target.

 

[garandman]

For those that got sidetracked on the whole equal energy thing, let me remind you that the OP's question was entirely about effect, does it matter in terms of what happens at the target.

The amount of energy in each kernel is the primary driver in how much a single kernel has an effect and matters at the target.

And the best way to decide that issue is to load up some ammo and go shoot at a target, And read your chronograph and target, rather than to conduct theoretical discussions.

 

[BoydAllen]

The amount of energy in each kernel is the primary driver in how much a single kernel has an effect and matters at the target.

And the best way to decide that issue is to load up some ammo and go shoot at a target, And read your chronograph and target, rather than to conduct theoretical discussions.

The last part is entirely correct. The first ignores the obvious significance of the ratio between the energy of one granule and that of the entire charge.

 

[garandman]

The last part is entirely correct. The first ignores the obvious significance of the ratio between the energy of one granule and that of the entire charge.

No it doesn't. Have a nice day.

 

[Alex Wheeler]

I posted a pretty good example of pretty large poi shifts for a .1gn change in powder charge above. Thats not ideal, we all want that barrel that puts everything into the same hole but it does not always work that way so being able to control things to a fine level is important. Theres a current IBS 1k group agg. record set with a barrel that had no seating depth window. It shot at .006" in, not .005 or .007 but .006 in. Was that a great barrel? No, but its owner was good enough to keep it in tune and set a record. The point is, Id rather be in control of as much as I can even if it does not matter in every barrel. Many times people point to short range BR as a way to convince people that you can get away with slop in reloading. Well, the SR group guys I know personally that are competitive are not sloppy. They maintain the same precision as lr guys in most aspects. I dont know any that are ok with +/- a tenth in powder charge or +/- .001" in seating depth or shoulder bump, ext. I think its just that they dont get on here and post what they are doing since its a competitive game which leads to alot of assumptions or old school thought.

 

[adamjmac]

Testing for small effects is incredibly difficult. You would have to fire hundreds of shots in controlled conditions to be able to measure the effect of a single kernel of powder.

All groups fired are random samples and no conclusion can be drawn for the root cause of a difference between two groups without first showing that the result was not random chance.

The effect of a single kernel of powder on the mean is very predictable because the physics and math behind it are pretty straightforward.

 

[tom]

Here's a 1,000 yard "ladder" ran round Robin over around a 30 second time frame for all shots. I guess the answer could vary, depending on where you are within the tune. This is a 6 bra with h4895, so each increment is about 6 kernels.

Tom

 

[dcali]

It's not hard to see the impact of barrel vibrations on vertical. This is why we do ladders. If you run the numbers through a ballistic calculator, you will find that you can predict the change in vertical impact as you increase velocity. What the calculator will tell you is that as your velocity increases, you will get a smooth upward trend of the POI.

BUT...

Those predictions will not match what you see on the target because they ignore the barrel vibrations. What you will see is steps. Increasing velocity will not result in any vertical change, and then all of a sudden it steps up dramatically. Then another step, and another. This is because of barrel vibrations - we want to wind up in the middle of one of those steps. Being on the edge of a step will leave you with painful amounts of vertical that is extremely sensitive to velocity.

The vibration of the barrel plays as big of a role as velocity variation. And while with enough time, money and effort, I'm sure you could calculate that, it's not practical at all. You just have to test it and see what happens. Sometimes you're lucky and you get a nice wide ladder step that is relatively insensitive to velocity. Sometimes, it's a tighter window.

I would venture out on a limb and say that it would be pretty rare to need to measure to a kernel. That said, it's not terribly hard to do with the right gear and it won't hurt anything.

 

[INTJ]

Please remember that what may not be important in an F-Class rifle can be VERY important in LR BR. We routinely shoot 5-shot groups under 3" and 10-shot groups under 5" at 1000 yds. We typically shoot a five shot string in under 20-30 sec and a 10 shot string under 35-45 sec.

In LR BR, because we shoot our shot strings quickly, we have a much better chance of keeping all our shots in the same condition. When that happens then very small things start to matter. I can show repeatable changes using .2 grain powder increments in a 300 WSM and .1 grain increments in a 6 BRA with tuning ladders shot round robin style at 1000 yds.

With an F-Class rifle, an extra .1 MOA may not have any effect and is overwhelmed by having to shoot slow and make a wind call for every shot. So it makes sense for F-Class shooters not to obsess about the nth degree of tuning but to obsess over wind reading.

In LR BR, while wind reading is very important, we don't need to obsess over it. We need to obsess over tuning as even .05 MOA--roughly half inch at 1000 yds--is a VERY big deal.

Here is a pic of round robin tuning ladders at 1000 yds. This is a 300 WSM. Notice that .2 grains is indeed making a difference.

 

[RegionRat]

...Adam,

Please remember...

Okay but looks more like an agreement.... than Adam needing to be reminded.... but he can speak for himself...

The importance you are pointing out to the beginners is on point, ... that the context of BR is vast and sometimes includes state of the art, which may or may not apply across the board, especially when the discussion is on the value of charge accuracy and tuning accuracy.

Sometimes, out of context remarks on the forum lead to confusion, especially the ones where charges are thrown without concern without words to explain why those can be done and where they should not.

 

[INTJ]

Okay but looks more like an agreement.... than Adam needing to be reminded.... but he can speak for himself...

The importance you are pointing out to the beginners is on point, ... that the context of BR is vast and sometimes includes state of the art, which may or may not apply across the board, especially when the discussion is on the value of charge accuracy and tuning accuracy.

Sometimes, out of context remarks on the forum lead to confusion, especially the ones where charges are thrown without concern without words to explain why those can be done and where they should not.

Good point. Adam and I have discussed this before where we talked about what is important and what the focus should be in loading. Without that context it makes no sense to reply to him so edited my post.

 

[adamjmac]

Each person in this thread has a different point of view, different experiences, different opinions and is asserting that a different thing is important.

I'm pretty sure we can agree that 1 kernel doesn't matter.

I'll leave it be.

 

[RegionRat]

In his post #73, Adam touched on another very important point in research and method that is the key to the single kernel discussion, i.e., when the specific effect of a single tiny variable change would require very careful experimental discipline to tease out of a large complex multi-variable system.

Finding a needle in a haystack experimentally isn't for everyone, just like F-Class or LR BR isn't for everyone.

 

[thejamesd]

The anal side of my OCD says 1 kernel is everything.

And....... thats why your paint jobs are perfect!