Klem Wrote:Playing Devil's Advocate to this guy's experiment - The point downrange where the bullet enters the radar's arc is important. Where is the radar when he shoots prone? Is the radar exactly the same distance from the gun? He also brings his hand forward and shifts the arc when shooting from the bench. These variables will also account for a 20fps difference in muzzle velocity.
His experiment is repeatable so I will do the same and post.
Notice the low-mounted tripod to maintain consistent Radar Field of Regard for projectile tracking. Same tripod set-up for on top of the bench, as well as the ground. Muzzle position didnt change on the bench, and the fps difference was also observed on the bench shooting with vertical torso vs choked up/recoil-managed torso.
The Radar track just confirms the known applied physics though. A vertical brace of variable resistance will have less resistive force to an arched brace, or an aligned brace behind the recoiling mechanism.
You see it especially in CQM stance.
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Zeneffect Wrote:How many rounds down range with satterlee total in this test? Trying to follow it, and it's a hard read to me.
I had 45 round count. Im not done and I probably wasted a few. There is a pile of videos on 10 round load development. Bolt action reloading has good data and good results but he talks extremely fast and is hard to follow. He does numerous videos and rifles on it.
SCJim Wrote:One old timer told me that if you see a decrease that indicated overpressure and the velocity decrease was due to case stretching and th eprimer leaking and or backing out. That's just hearsay of course. I have never seen more powder equal less velocity but never have I seen a linear correlation either. I have been basing my load development for several years now on looking for flat spots in th epowder/velocity curve and loading to the middle of those to give myself some leeway on temperature and charge measurement accuracy. I have no idea why adding .3 gns of powder at one stage can give a 50 FPS gain velocity and the next .3 increase will only give a 5 FPS increase. But those 5FPS nodes give me the best load performance
I saw some satterlee videos testing different primers. Loads with magnum and bench rest primers had a more constant velocity curves and normal primers don't. I did similar satterlee tests myself and came up with similar results. So satterlee seems to work better with standard primers.
It is possible at different powder fill/compression ignition may differ, it is possible to add .3 gr of extra powder only for it all to exit the barrel without burning. Unburned powder is absorbing energy that could make the bullet go faster, so it is possible to add power and get less velocity with poor ignition. Best ignition seems to be 97% to 100% fill from my experience.
Jimla Wrote:so it is possible to add power and get less velocity with poor ignition.
Have you seen this with your own eyes?
And if you have, can we repeat the test to see if we get the same results?
I agree, when you zoom in the powder/velocity curve is rarely exactly a straight line. That in some sections it appears elastic and in other sections, inelastic. That if the curve is repeatable that Satterlee encourages us to focus on the elastic sections to hone our load. But it never goes backwards. Putting more powder in never goes backwards than a lesser load. It might be an elastic increase, but never less velocity.
Another reason why the curve is never straight is Normal distribution. At each load increment there will be a range of velocities in a Normal curve. Each time you fire that load, the velocity can be anywhere on that range according to the probability represented by the shape of the distribution (as reflected by the standard deviation). The point being, in shooting we rarely get exactly the same velocity each time we pull the trigger, even if we are careful and have good equipment. We must not then see these subtle variations in velocity as indicators of precision, unless they are (1) repeatable, and (2) it actually translates into smaller group sizes.
Anyone therefore claiming to only need 10 rounds across a chronograph to figure out the best load is deluding themselves. Plus, ignoring results on target is also delusional as this is ultimately what we are trying to do - find a load that gives the smallest groups. Regardless of what velocities we're getting the barrel will be whipping around and contributing to where the bullet goes.
Here is a graph of the ladder that he shot in the video. The red lines are where he chose to start his test rounds (50.4gr and 51.5gr). What he calls the middle of the nodes are 50.4gr and 51.6gr, which is at the peak. The higher velocity red mark is near max so he moved it back .1gr to be safe as he was trying to find the max load for a new cartridge he was working on.
Since the above video he has modified his method slightly and everything I can find recently he starts where the SD/ES is the best and then goes .1gr-.2gr on each side. Also he is still looking for a velocity(pressure) node that correlates with the SD/ES. One thing he says in the video above is that he is more concerned with ES than with SD. Keep in mind that he is going to be shooting at 1000yds(or less-PRS) so that is what he is developing his loads for. He also claims that his best loads have always been found using this method first.
I haven't really delved into his 2.0 version as deep as I want as I am going to try Eric Cortinas method when I get my rifle back.
This is a good graph because it shows the velocity dropping in defiance of what we would expect. We expect more powder = more velocity, and that is the conventional premise. But, he loads 50.6gn and gets a lower velocity than lesser loads; how is that explained in light of the convention?
Even if we can't explain it, for this to be scientifically valid his results need to be repeatable. If he loads those amounts again and gets the same results then that is a good thing. If he gets a different curve then the test is invalid. 10 rounds is not enough to reveal your barrel's idiosyncrasies.
I have to go with Klem on this one, in the main. The biggest operative imo for curve deviations in a single-shot ladder is the normal distribution occurring at each shot load. At the top end, looking at the curve just above here, I would say the charge is getting compressed causing powder ignition/burn to vary and a resulting slower exit MV -- either that or again, distribution-variation of MV at that charge.
Now I do use a single shot ladder to begin most of my load developments but don't think for a minute that 10 shots will tell me the whole accuracy story for my barrel and the powder/bullet/primer/brass story. Rather this string establishes the overall powder curve response for my specific barrel to the combo particulars.
I graph my results and then, to weed out at least some of the distribution deviations, will curve fit the powder response along with the curve of "book" powder for comparison. The slopes of the 2 curves should be close to each other even though the curves will differ on actual MVs... This then tells me where I want to concentrate development to find the nodes. Overall it takes me somewhere 30-50 rounds to identify my desired load.
Primer type, powder lot, barrel length (vs "book length"), internal friction characteristics, brass differences, plus more variables, some controllable, some not - you work with what you have.
I would find it highly unlikely (well nigh impossible) to ever see a completely linear (in Klem's terms, elastic) powder-MV graph due to all the variables plus some measuring uncertainties. I'm not a benchrest shooter nor as good a shooter as some of you guys but the physics and mechanics of the internal ballistics, coupled with all the uncertainties which are never quantified, these all militate against thinking you will find your perfect load in 10 shots.
ps one other thing going unmentioned, and this is just a theory of my own, is that premium barrels will probably show less distribution/variations than rack grade if only b/c they have a much more premium, controlled and quality-oriented production rigor. But that's just a theory of mine. Satterlee's stuff could also be making advantage of this effect as he is concentrating on prs/1000-yd matches, those guys don't use the rack grades we oft-times have.
I would venture to say that if any 10-shot string were repeated under similar, controlled circumstances at close-to-same-shotcount (for barrel internal similarities), you would see an oscillating string with different peaks/valleys from the first string you shot. Hopefully they would overlap each other... and theoretically, after several of these overlapping strings, the wide-varying MV's/powder charges and the narrow-varying MVs/powder charges (ie, "nodes") would become evident. I have yet to see anyone do this several-string test and have yet to see the graphs/data, but mechanically that's what I would expect.
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The term 'elastic' is not mine, it describes different angles of a graphed linear relationship. Elastic is a more horizontal line, and inelastic is a more vertical line on a graph. Like these graphs from economics.
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Satterlee is looking for the flatter or elastic/horizontal parts of the relationship between powder and velocity.
O yes, right... those econ guys... making the independent variable (price) go vertical, contrary to any purist-math guys...! Inverted functions. Or maybe I'm wrong, whatever (econ-wise). I remember that from there now. Way I would call it is whether the MV/charge variation is more linear vs non-linear. Within boundary conditions, MV vs powder charge should be linear in a perfect world.
At any rate, with powder grains as the horizontal independent variable, a flatter line, if not due to statistical-distribution issues, would mean no or very little MV change for a powder change in that region. Which, to me, sounds great but in theory should not occur since more powder means more pressure-gas generation-more energy to push the bullet and accelerate it. But you could take it to mean that for your particular measuring technology at your bench, whatever small powder variations that occur in your measures would not affect MV very much. Uncertainties and uncontrollable variables could and probably will mask/obscure that, however...
If somebody wants to use the 10-round method, fine by me. But I have no plans to do it.
"Down the floor, out the door, Go Brandon Go!!!!!"
One more thought, and it's just my observation again...
Once I plot the single-charge ladder that I did and its curve fit, I look at them to see which MVs are "far away" from the curve fit. A larger vertical dispersion from normal at that point, suggests to me that it is "far" off of any node, since by definition a node's MV response will be tight, low SD and low ES for any cluster of shots at that load, therefore "close" to the curve fit. So an MV point with a large spread away from norm, is off-node. But at that specific point, mathematically/graphically the actual MV curve will tend to be "flat." Since the response will by definition curve back towards the linear fit (concave and convex parts of the actual curve will by definition have a flat, or zero, slope at those points), thus there will tend to be a flat-looking section... but to me it would seem to be just the point that I do NOT want.
Like I said however, if it floats your boat to do it that way, fine by me.
"Down the floor, out the door, Go Brandon Go!!!!!"
single shots per load are good enough to get a rough idea for velocity and pressure signs and I suppose to get a rough idea for the curve. But even for rough load development I prefer 3 minimum or 5 shots per increment depending on component availability.
On that graph in post 84 I would be loading 10 or 15 rounds @ 50.6, assuming that 2975 - 3000 FPS would be sufficient velocity to get the job done and exhibited tight grouping to use as a second check. Then if the load behaved adjust seating depth in or out to refine the grouping and possibly experiment with different flavors of primer also if needed and possible. I love those big flat spots where you can vary the load by a couple of tenths of a gn and still be in the node. You can load to the middle and shoot from 20F to 95F with little or no charge adjustment needed
SCJim Wrote:On that graph in post 84 I would be loading 10 or 15 rounds @ 50.6, assuming that 2975 - 3000 FPS would be sufficient velocity to get the job done and exhibited tight grouping to use as a second check. Then if the load behaved adjust seating depth in or out to refine the grouping and possibly experiment with different flavors of primer also if needed and possible. I love those big flat spots where you can vary the load by a couple of tenths of a gn and still be in the node. You can load to the middle and shoot from 20F to 95F with little or no charge adjustment needed
That is what he does as his next step, which is in another video, but he does skim over what he would do next in the first video.
08-15-2022, 03:52 PM (This post was last modified: 08-15-2022, 05:58 PM by Harpoon1.)
SCJim Wrote:single shots per load are good enough to get a rough idea for velocity and pressure signs and I suppose to get a rough idea for the curve. But even for rough load development I prefer 3 minimum or 5 shots per increment depending on component availability.
On that graph in post 84 I would be loading 10 or 15 rounds @ 50.6, assuming that 2975 - 3000 FPS would be sufficient velocity to get the job done and exhibited tight grouping to use as a second check. Then if the load behaved adjust seating depth in or out to refine the grouping and possibly experiment with different flavors of primer also if needed and possible. I love those big flat spots where you can vary the load by a couple of tenths of a gn and still be in the node. You can load to the middle and shoot from 20F to 95F with little or no charge adjustment needed
+1
If Im trying a new powder, case, primer combo, I usually just do a 10 round ladder test to see if theyll work together and find some likely areas to investigate. If Im already familiar, with accuracy nodes around 3% of charge weight apart, then usually 5-6, 3 shots groups can isolate what Im looking for!
The 10 round ladder is only a starting point, not the end result!
Satterlee has refined his technique even more, heres the latest version I can find!
If Im trying a new powder, case, primer combo, I usually just do a 10 round ladder test to see if theyll work together and find some likely areas to investigate. If Im already familiar, with accuracy nodes around 3% of charge weight apart, then usually 5-6, 3 shots groups can isolate what Im looking for!
The 10 round ladder is only a starting point, not the end result!
Satterlee has refined his technique even more, heres the latest version I can find!
Been using ladder testing for years (optimal charge weight). 1 shot and 1% jumps (about .2gr in the Grendel and about 1gr in the RUM) from starting load to max.
I am looking for when multiple shots in a row group together. Then I focus on development around that charge weight for accuracy.
Dt219 Wrote:Ok thanks guys. I feel like I should just sell the magnetospeed and buy another chrono. It works fine but it trashes my groups. Would be nice to get group size and data in one trip. I was careful loading and recording the data. The only thing that could have possibly happened is rounds maybe out of order. Dont see how it could have happened.
08-22-2022, 09:52 AM (This post was last modified: 08-22-2022, 10:04 AM by Dt219.)
Remington Jim Wrote:LabRadar - I love mine ! RJ
I finally got mine rigged up on the side of the guard at the 9:00 position. I find it very easy to make a mount for it but very difficult to get the spacing off the barrel correct. I Missed the first shot but have not missed another one in 50 rounds at least. Ill stick with it now since I can do both.
![[Image: Ladder4.png]](https://i.ibb.co/YLyKSr9/Ladder4.png)
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RJ