ES of slower powders

[Doom]

Statistically speaking ES has no value and way too much is made of it. Regardless of the number of rounds tested it represents only two shots, and in a statistically valid sample it should have almost no impact on the SD.

If the ES is low on a 5 round sample, then its possible to infer that that the loads are consistent but beyond that it means nothing, other than the ES values make up 40% of the mean and SD values. If the sample is 20 rounds the ES values make up only 10%, and have a much lower impact on the SD. In the real world the ES will increase as the number of rounds tested increases, but the SD may increase or decrease but to a much lessor extent.

To the OP's question, trying to compare ES between two different powders is somewhat akin to trying to compare the velocity between two powders based on 2 shot samples. What you see in the numbers is real, but what that means is very little to nothing about the real tendencies of the powders.

 

[gunsandgunsmithing]

Mike, the part about a tuner increasing amplitude is interesting. Any of my experiance adding a mass to the muzzle has reduced amplitude at the target. Poi shifts less vertically across charges. Where a lighter contour barrel has a larger amplitude at the target, much more vertical poi shifts across charges. Any thoughts on that?

I can't explain what you've seen. I can say that I've seen just the opposite both on target and on an oscilloscope. If you think about it, the bbl is already deflecting more with a mass at the end even before you pull the trigger. An extreme example is some rf br rifles may have a huge 1lb tuner on the end of a .850 straight bbl. You can literally see the bbl bounce when you close the bolt. Not conducive to shooting fast.
Some rf shooters actually count in their head between shots, a cadence.

 

[CharlieNC]

The predominate frequencies for positive compensation which result in a tuning node are in the 5-20 kHz range, not the much lower frequencies which are highlighted by the finite element barrel calculations. While the Chris Long optimum barrel time concept is associated with unstable muzzle diameter expansion, the associated barrel times are in this frequency range which is why the method works well in many cases. More to come on this later......

 

[gunsandgunsmithing]

The predominate frequencies for positive compensation which result in a tuning node are in the 5-20 kHz range, not the much lower frequencies which are highlighted by the finite element barrel calculations.

Agreed. I was pointing out extreme examples that were both outside of the frequencies we're most interested in but it was to make a point. I still dont want to shoot while the bbl is bouncing like a pogo stick though.

I've gotta get ready for a match but I'll check in as I can on this discussion.

 

[Alex Wheeler]

I can't explain what you've seen. I can say that I've seen just the opposite both on target and on an oscilloscope. If you think about it, the bbl is already deflecting more with a mass at the end even before you pull the trigger. An extreme example is some rf br rifles may have a huge 1lb tuner on the end of a .850 straight bbl. You can literally see the bbl bounce when you close the bolt. Not conducive to shooting fast.
Some rf shooters actually count in their head between shots, a cadence.

I have made stocks soft enough to bounce like that. Interesting stuff, you would not think they could shoot like that but they do. Just so I am understanding you, your saying that when you hang a tuner on the barrel you will see a larger shift in poi across powder charges and a smaller poi shift on light sport barrels vs heavy contours?

 

[Straightshooter1]

For many months now, I've been trying to wrap my head around the harmonics of a barrel and how they are initiated and affected by the various inputs from the whole platform from the moment of ignition to the exit of the projectile. It's just my natural insatiable curiosity at work. And this discussion regarding frequencies and amplitude is just what I've been focused on lately and finding the comments helpful.


Question to you gunsandgunsmithing, increasing amplitude doesn't by itself change a frequency . . . right? As I understand it, when something like a tuner is put on the end of a barrel that weight on that point of the barrel is going to change both amplitude AND frequency. But there's no direct correlation for the amplitude effecting frequency, huh? Though I get it that there are various resonance frequencies involved with any shooting platform and a tuner in of itself has a resonance frequency that will interact with that of the barrel's to some extent.

In the end, it's the net effect we get on paper that counts.

 

[gunsandgunsmithing]

Ccorrect. Amplitude and frequency are independent of one another.

 

[gunsandgunsmithing]

I have made stocks soft enough to bounce like that. Interesting stuff, you would not think they could shoot like that but they do. Just so I am understanding you, your saying that when you hang a tuner on the barrel you will see a larger shift in poi across powder charges and a smaller poi shift on light sport barrels vs heavy contours?

No, that's not what I'm saying. Tuners and powder charges are two separate things. And no, I'm not saying that you'll see less amplitude change on a stiffer bbl than one that's less stiff. Sorry if I said anything that implied that. It's not the case. Putting a mass on the end of the bbl will increase amplitude for a very short period of time, regardless of stiffness but ultimately the amplitude will reduce faster than without that mass. We're only worried about that very short period while the bullet is in the barrel.
Tuners will change poi on any barrel..if it's working. That's what we're doing, to a degree...moving the sine wave to coincide with bullet exit by changing the frequency a tiny amount.

 

[Alex Wheeler]

Ok, what I am getting at is that amplitude is easy to see on a 100 yd target when increasing powder charge (exit timing). I look at the highest poi vs the lowest poi of the wave as the size of the amplitude, at least the amplitude of the main harmonic that effects the bullets flight. When I hang a weight (tuner, solid mass, suppressor, ext) on a muzzle that amplitude gets smaller. When I shoot a sporter that amplitude is quite large. I am sure theres many things you can measure, Im just talking about what I can see on target. Thats why I was confused by your statement.

 

[gunsandgunsmithing]

Ok, what I am getting at is that amplitude is easy to see on a 100 yd target when increasing powder charge (exit timing). I look at the highest poi vs the lowest poi of the wave as the size of the amplitude, at least the amplitude of the main harmonic that effects the bullets flight. When I hang a weight (tuner, solid mass, suppressor, ext) on a muzzle that amplitude gets smaller. When I shoot a sporter that amplitude is quite large. I am sure theres many things you can measure, Im just talking about what I can see on target. Thats why I was confused by your statement.

 

[gunsandgunsmithing]

Just trying to keep myself straight here but, we have to remember that frequency and amplitude are two separate things. Increasing powder charge doesn't change frequency but does change amplitude. Think of hitting something with a bigger hammer. Powder charge also changes how long the bullet is in the bbl. Remember, we've done nothing to change frequency. Frequency is just a fancy word for time between nodes. For all intents and purposes, frequency is a constant at this point.

Now we get to tuners. They work just the opposite. Forget about amplitude for a minute, it later becomes a "constant". But by means of moving the tuner, you manipulate frequency and frequency is the main factor here when we're talking about timing bbl position with bullet exit.

The biggest part that amplitude plays in tuning is that more amplitude at the bbl translates to bigger groups at the target..when NOT in tune. That sounds like a bad thing but I like it because it tells me more clearly that the gun is or isn't tuned...on target. A short, stiff barrel is harder to see tune with than a less stiff bbl. I think this is what you are getting at with sporters showing more amplitude. That is correct but carries it a bit further than I'm comfortable with. In really good conditions, it's not hard to tune either, but when the wind and reality of shooting competitively come into play, I prefer a barrel that "talks to me" more clearly.

Case in point, I've moved mostly to my own contour that is simlar to a LV and away from stiffer barrels. Stiffer barrels are good in other areas and for different reasons, but as far as reading tune in the real world, I prefer a little less stiffness. That's amplitude.

Now, the benefit of amplitude beyond all that is that the arc is taller but remember, the nodes are frequency dependent. So, we have the same frequency(time between nodes) yet a taller arc, per se. That's how amplitude actually widens the tune window. Now remember, we have the same time between nodes(frequency) but a taller sine wave(amplitude)..So the barrel is spending more time where we want it and less time where we don't, because the speed at the "scatter node", which is technically the node(that's a different discussion). Suffice it to say that we want bullet exit at top or bottom, not in the middle.

Since the frequency is the same but the arc is taller, it spends more "slow time" at top and bottom but less"fast time" traversing the out of tune area. I hope that makes sense to you..or somebody.

 

[Alex Wheeler]

I get all of that. I have had a few guys on different contours for a few years, my mind is not yet made up here yet. I also agree the frequency is relatively a constant since I have never been able to do anything to change distance between nodes. I suspect a tuner does not change frequency since the node spacing stays the same but it moves that frequency wave in relation to the amplitude wave if that makes sense, so you can move the accuracy point but not the spacing. But Im getting away from what we are talking about. Im not talking about tuning with a tuner. Im talking about this statement of yours, "A tuner(mass) at the end of the barrel literally does create more muzzle deflection and a wider arc(amplitude) while the bullet is still in the barrel". What I am saying is if I run a series of groups over a certain powder charge window, then do it again with a tuner/mass/suppressor/ext. hung at the muzzle the target will show less amplitude with the mass than without. I know you have done testing here, so I am trying to figure out if our terminology is different or the measurements do not necessarily match the target. Im not challenging your statement just trying to understand it.

 

[Straightshooter1]

Just trying to keep myself straight here but, we have to remember that frequency and amplitude are two separate things. Increasing powder charge doesn't change frequency but does change amplitude. Think of hitting something with a bigger hammer. Powder charge also changes how long the bullet is in the bbl. Remember, we've done nothing to change frequency. Frequency is just a fancy word for time between nodes. For all intents and purposes, frequency is a constant at this point.

Now we get to tuners. They work just the opposite. Forget about amplitude for a minute, it later becomes a "constant". But by means of moving the tuner, you manipulate frequency and frequency is the main factor here when we're talking about timing bbl position with bullet exit.

The biggest part that amplitude plays in tuning is that more amplitude at the bbl translates to bigger groups at the target..when NOT in tune. That sounds like a bad thing but I like it because it tells me more clearly that the gun is or isn't tuned...on target. A short, stiff barrel is harder to see tune with than a less stiff bbl. I think this is what you are getting at with sporters showing more amplitude. That is correct but carries it a bit further than I'm comfortable with. In really good conditions, it's not hard to tune either, but when the wind and reality of shooting competitively come into play, I prefer a barrel that "talks to me" more clearly.

Case in point, I've moved mostly to my own contour that is simlar to a LV and away from stiffer barrels. Stiffer barrels are good in other areas and for different reasons, but as far as reading tune in the real world, I prefer a little less stiffness. That's amplitude.

Now, the benefit of amplitude beyond all that is that the arc is taller but remember, the nodes are frequency dependent. So, we have the same frequency(time between nodes) yet a taller arc, per se. That's how amplitude actually widens the tune window. Now remember, we have the same time between nodes(frequency) but a taller sine wave(amplitude)..So the barrel is spending more time where we want it and less time where we don't, because the speed at the "scatter node", which is technically the node(that's a different discussion). Suffice it to say that we want bullet exit at top or bottom, not in the middle.

Since the frequency is the same but the arc is taller, it spends more "slow time" at top and bottom but less"fast time" traversing the out of tune area. I hope that makes sense to you..or somebody.

It all makes perfect sense to me and well said IMHO. It's exactly how I've come to understand it after months of contemplation. lol. . . I wish I could have found this explanation beforehand to save me some time and an aching brain.

 

[gunsandgunsmithing]

I get all of that. I have had a few guys on different contours for a few years, my mind is not yet made up here yet. I also agree the frequency is relatively a constant since I have never been able to do anything to change distance between nodes. I suspect a tuner does not change frequency since the node spacing stays the same but it moves that frequency wave in relation to the amplitude wave if that makes sense, so you can move the accuracy point but not the spacing. But Im getting away from what we are talking about. Im not talking about tuning with a tuner. Im talking about this statement of yours, "A tuner(mass) at the end of the barrel literally does create more muzzle deflection and a wider arc(amplitude) while the bullet is still in the barrel". What I am saying is if I run a series of groups over a certain powder charge window, then do it again with a tuner/mass/suppressor/ext. hung at the muzzle the target will show less amplitude with the mass than without. I know you have done testing here, so I am trying to figure out if our terminology is different or the measurements do not necessarily match the target. Im not challenging your statement just trying to understand it.

I dont think we've been on the same page. Again, powder charge and a mass on the end of the barrel are two different animals. But..if I'm on the same wavelength with you now, it can be explained by the dampening characteristics of having a mass at the end of the barrel vs not. That's a different story but yes, it might be relative to what I think you're trying to describe.
My tuners incorporate features that are there specifically to do just that, but even a solid mass dampens.

I try to convey things in terms that most of us can understand. That's a good indicator of someone who understands what they are talking about. But I first have to understand the question and you have to realize that changing charges makes for a moving target for me. It may be as simple as me misunderstanding your question, so I apologize in advance. I think we're talking apples and oranges. But you can't change the size of the hammer(powder charge), and then compare it to a tuner. It's just two different things with two different affects.

 

[Alex Wheeler]

I think what you describe as dampening is what I see as amplitude reduction. I just do not see how you can have an increase in amplitude and a more stable poi, seems like opposites.

I think we are on different pages. When I speak about amplitude I am talking about all a barrel can give. That means across a giving charge window. If I am dealing with a thinner barrel it will have a larger amplitude on target than a thicker one. It will shoot well in tune but have more vertical dispersion than the thicker barrel when out of tune. Node widths are the same because frequency is the same but the sporters gets more ugly as it goes out so it seems like they are smaller.

 

[gunsandgunsmithing]

I think what you describe as dampening is what I see as amplitude reduction. I just do not see how you can have an increase in amplitude and a more stable poi, seems like opposites.

I think we are on different pages. When I speak about amplitude I am talking about all a barrel can give. That means across a giving charge window. If I am dealing with a thinner barrel it will have a larger amplitude on target than a thicker one. It will shoot well in tune but have more vertical dispersion than the thicker barrel when out of tune. Node widths are the same because frequency is the same but the sporters gets more ugly as it goes out so it seems like they are smaller. In the end I guess it doesnt matter. I just go by the targets. We dont learn on the keyboard.

I agree with most of that but I'm not sure how changing powder charge can be correlated to what a tuner does to amplitude. When you change powder charge you're changing several things at once, like trajectory, amplitude and in bore time. I dont see how you can compare the two.

If you run the same powder charges before and after a tuner in the same gun, conditions and tuner settings to come to your conclusion, then its dampening. I can assure you that amplitude is increased with a tuner on the end of the barrel while the bullet is in the barrel. That much I'm positive about.

 

[HTSmith]

also made an offhand hit at 1300

Dude should be buying lottery tickets.

 

[CharlieNC]

I think what you describe as dampening is what I see as amplitude reduction. I just do not see how you can have an increase in amplitude and a more stable poi, seems like opposites.

I think we are on different pages. When I speak about amplitude I am talking about all a barrel can give. That means across a giving charge window. If I am dealing with a thinner barrel it will have a larger amplitude on target than a thicker one. It will shoot well in tune but have more vertical dispersion than the thicker barrel when out of tune. Node widths are the same because frequency is the same but the sporters gets more ugly as it goes out so it seems like they are smaller. In the end I guess it doesnt matter. I just go by the targets. We dont learn on the keyboard.

What you are trying to offset exactly is the rate of rise in point of impact vs velocity increase, with a matching rate of decrease in downward muzzle harmonics which is a combination of frequency and amplitude. I am finishing a straight forward procedure to characterize this, and will report soon.

 

[Alex Wheeler]

What you are trying to offset exactly is the rate of rise in point of impact vs velocity increase, with a matching rate of decrease in downward muzzle harmonics which is a combination of frequency and amplitude. I am finishing a straight forward procedure to characterize this, and will report soon.

Doing it 100yds minimizes most of the velocity related poi shift. The discussion never ends, but its pretty simple to see on target results.

 

[INTJ]

No I don't worry about it at all. It will work itself out. If you do all the testing you should be doing you will end up with an accurate load and the es will be what it is. I have hunting rifles that group 3" at 1k in the 20s for es. Different primers will lower the es and make the group bigger. Every bench gun I have tuned will end up with es in the teens usually. Only a couple tenths away is single digits and bigger groups. I tune every thing at 1k and really have never seen best es and groups line up. So if they do not correlate why look at them? That said your not going to end up with crazy es if you tuned the rifle for accuracy. With good practices and good components and a well built rifle you just dont see crazy es to begin with.

I think there is a difference between saying that the best ES usually doesn't line up with the best group vs ES doesn't matter. I too see that all the time, where my best group does not have the best ES.

However, I have seen very good close range groups with ES in the 50s. I don't trust a load like that and have never taken such a load to 1000 yds. My assumption is when the ES gets into the mid-20s and above that I'll see vertical at long range. I have never tested that.

Almost always, I find that good loads have ES in the mid 20s or less. So for me, a bad ES with a good group shows me that more tuning is needed.

That leads me to my question. Have you ever seen a load with an ES of say 50 shoot a good group at long range?