Enjoy gents .
Just released.
Tim Sellars - Positive Compensation | #92
Just released.
Tim Sellars - Positive Compensation | #92
-
Having trouble using the site?
Contact support
Positive compensation and its explanations .
- Thread starter timintx
- Start date
I watched this yesterday, and found it hard to follow because of the way the information was presented.
I did think the part about tuning for a set distance was interesting- but I had trouble following his explanation about what that caused at shorter ranges and how to calculate it with a ballistic calculator. I'd probably need a third watch of that section.
I did think the part about tuning for a set distance was interesting- but I had trouble following his explanation about what that caused at shorter ranges and how to calculate it with a ballistic calculator. I'd probably need a third watch of that section.
Well I know there is a lot to it but if you need any help understanding let me know . I will do my best to clear it up .
Timintx
Tim a guy I shoot with Lynn in California says he is your biggest fan.
Billy "The Kid"
Billy "The Kid"
Ok , well let me better describe the calcs on the ballistic program. When you take two shots and record each velocity say at 1000 yards. On the ballistic program go to the numbers graph on the program, and look at inches of drop at 1000 yards with each velocity recorded and note the difference. So that is what I call the calculated drop for those two velocities . let say the the difference you calculated is 5.6 inches difference of vertical impact with the 2 different recorded velocities. Then your actual shots you took had a difference of 5.6 inches of vertical which matched your calculated vertical, by that you can say your barrel is not bending when the bullets are exiting. So if you shot inside of that your barrel is moving up hence Positive compensation. If the actual drop is is actually 10 inches being way more then the calculated vertical then you barrel is moving down exaggerating the vertical which would be Negative Compensation. Hope this helps sir.
Timintx
Last edited:
Sure ,these are actual shots from the target super imposed on my computer for filing , Then the targets are are thrown in to a ever growing pile of others.
Timintx
Attachments
It was easy to follow and understand great job Tim
Thanks Tim, that makes sense - I'm almost never using or looking at the drop graph, so I was initially comparing come-ups.
I turned the transcript on the side window, and it makes it easier for me to understand and string the points together.
I'd like to give this one a test. Earlier this year I stumbled into something similar with my AR-15 for PRS gas gun and I need to look a little deeper into it, or from a different perspective. I'd like to test this in a bolt gun, though, just to get rid of the "noise" that AR's like to dish out...
Anyway, the gist of it was that I strapped successive steps of weight near the muzzle of my AR-15, and saw non-linear changes in vertical POI with incremental weight added. I was looking to get better dispersion and that didn't happen so I didn't dig any deeper, but this seems simple enough to approach in the 200yd tunnel with a shoulder-fired bolt gun. Good winter project.
I never saw any (notable) vertical POI shift from the accuracy fixture (rail gun, basically) in my previous testing, nor any trends towards positive nor negative compensation. Interesting to hear you say the same. I've heard a lot of talk about "tuning loads" for positive compensation and I'm extremely skeptical of that, but physically altering the mechanics of the barrel/rifle system seems much more plausible to me if it's to be a repeatable thing. If it's something that requires perpetual chasing, though, I don't find a ton of value in it outside of a square range.
ETA: dogshit groups and higher drag are a correlation I've seen many times, also.
Anyway, the gist of it was that I strapped successive steps of weight near the muzzle of my AR-15, and saw non-linear changes in vertical POI with incremental weight added. I was looking to get better dispersion and that didn't happen so I didn't dig any deeper, but this seems simple enough to approach in the 200yd tunnel with a shoulder-fired bolt gun. Good winter project.
I never saw any (notable) vertical POI shift from the accuracy fixture (rail gun, basically) in my previous testing, nor any trends towards positive nor negative compensation. Interesting to hear you say the same. I've heard a lot of talk about "tuning loads" for positive compensation and I'm extremely skeptical of that, but physically altering the mechanics of the barrel/rifle system seems much more plausible to me if it's to be a repeatable thing. If it's something that requires perpetual chasing, though, I don't find a ton of value in it outside of a square range.
ETA: dogshit groups and higher drag are a correlation I've seen many times, also.
I presume you mean BC, or is that a dig at shooter form? I live in low speed high drag.
I mean drag in the physics sense. Tangent to the topic so I apologize but I'd like to see the shooting world get away from BC altogether. It has some utility as a loose & quick reference for comparing bullets, but Cd solvers are the way forward in accurately predicting trajectories.
BC is like looking at the movie poster or the DVD box. Cd solvers are like watching the movie.
Excellent show. I had to watch it twice but I got it now. Erik seemed confused though.
I have targets and chrono ready to go - test tomorrow weather permiting. I use factory ammo and a Cortina tuner. so this should be interesting, especially the velocities.
@timintx I could never make sense of your username until today, Nor did I know who you were but Tim IN Texas. DUH. Anyways great video, IMO any rifle that shoots small groups at 1000 Yards is already tuned for positive compensation just not knowingly. As Cortina mentioned his 1.3" group at 1000 had ES of 20 fps.
These are what I was using. I'm turning the barrels to match nominal diameter for the clamps. Spacing can be set with a depth mic or caliper pre-set and held against the muzzle thread shoulder.
ETA: Not sure if this link is working, but they're 2-piece shaft collars.
McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
Ledzep
I have made shaft collars for each half ounce increment out of steel and aluminum to determine what weight the barrel needed.
If you look at the picture there is a section of aluminum thick walled tubing with a tapped hole for a setscrew.
I slide it over the barrel and lock it down then add the shift collars 2-3/4 inches from the muzzle.
Once you get two spaced shots touching at 100 your weight is close enough.
At that point you can either make or order your tuner.
I have made shaft collars for each half ounce increment out of steel and aluminum to determine what weight the barrel needed.
If you look at the picture there is a section of aluminum thick walled tubing with a tapped hole for a setscrew.
I slide it over the barrel and lock it down then add the shift collars 2-3/4 inches from the muzzle.
Once you get two spaced shots touching at 100 your weight is close enough.
At that point you can either make or order your tuner.
Attachments
If you have any hang ups I will be glad to help if I can .
Last edited:
A couple of days later than planned because of weather, I was able to run the tests. Two different lot #s of factory ammo. 10 shots each on separate water lines.
When the paper is compared to the velocities I must say you've definitely hit on something, specifically when it comes to using tuners. I got lots of very useful data.
Bottom line, I could actually see visually with shots on paper, not only how this works, but also what I needed to tune for. That worked too. I was able to quickly, roughly adjust the tuner before I had to quit shooting and the results were enlightening. Shots on paper responded to the tuner adjustments as you predicted.
I've been busy with other matters but will post more on the results in a couple of days or so days.
Great work Tim! Thanks!
EC is one of the biggest tuner advocates, but he admittedly has no idea how they work.
And if a precision "node" does in effect exist that you can tune for:
- is a tune consistent across different conditions, or does it need to be re-tuned with a change in atmospheric conditions?
- if it's positive compensation that's the driver behind a tune, then how helpful is that tune at a set distance over varying distances? Most of us here aren't BR shooters shooting at one set distance.
- how repeatable is a "tune" if you were to repeat the exact same tuning test over multiple days and conditions? Are the results consistent and repeatable?
Timintx has been an advocate of tuners for roughly 20 years now so ec is a relative newcomer to the tuner world
I don't know when EC got involved with tuners.
I do know he sells them, rabidly advocates for them, and has no clue how they work.
Ah yes. Secrets. Because it's a "dark art".
It's been widely published for 20÷ years now and you can go on the U S Patent website and read about the Browning Boss system from the 90's.
Jim Boatright who posts here has also written articles about tuners many years ago in precision shooting magazine.
Bill Calfee has been setting records with Hoehn/Harrels tuners for 30 plus years now and got the issue started with the benchrest crowd in the early 2000 time frame.
Jim Boatright who posts here has also written articles about tuners many years ago in precision shooting magazine.
Bill Calfee has been setting records with Hoehn/Harrels tuners for 30 plus years now and got the issue started with the benchrest crowd in the early 2000 time frame.
I know it is recommended that you use 1 grain increments when running this test but with smaller cartridges like a 6.5 creedmoor should it be run with smaller steps like .5 grains?
He knows how they work. He knows how to adjust them . He knows how to build them. He knows what they do . From day one you have gone in circles with your comments. What is your agenda ? Who are you paired with ? Why is it that you want tuners to not work ? What dog do you have in this fight ? Who is your buddy that you dont want to be wrong ? Who ass is your nose in ? Honest question. Why not just walk away.
That is fine but you will see less overall. for graphing too much resolution means the window you are looking in to is narrow so it is about spreading the different exit times just to see if something is going on in the lower speed ranges and the same for the 2 shot test. Then you can adjust the tuner to the right spot for a given powder charge . The beauty of a tuner is you can put the pattern where you want it instead of changing powder charge. I use one grain difference on my dasher for testing and worked very well. I want at least 36-50 FPS difference to graph and 2 shot tune with just to make sure I can see it .
I'm not paired with anyone.
Whether tuners work or not has no bearing on my fiscal situation.
And if you listen to EC on podcasts, he claims tuners work because "BR shooters use them" and claims to not understand the statistics and math behind them. I'm just taking him for his word.
Last edited:
The testing method you are doing is exactly what Bill Calfee and the rimfire guys were doing 20 years ago and it turns out that center fire worked exactly the same, so us center fire guys are playing catch up . You would be surprised how close they really are to each other , as a matter of fact they react exactly the same just with less amplitude due to recoil force verses relative stiffness.
It may be interesting to see what a 3 shot pattern shows. No reason to go higher or lower than those 3 because those aren't speeds I would run. I don't use a tuner so it is all about using powder to adjust the tune, then move to seating depth.
Bear in mind the main reason you would want to shooting different velocities and comparing point of impact is to see how the barrel is moving during your normal load of exit time .
Here we go Tim….
I have as couple of caveats before I go on though:
- This was a small test.
- That’s kind of a good thing in a way because I was still able to see cause and effect and thus the test saves ammunition.
- You will see the target below had aiming points on the water lines. That went out the window. I had trouble seeing them. even at 27X because we had a low, dark overcast moving from west to east with very brief lighter conditions where I could see them.
- So, Azimuth was all over the place because most of the time I had no aiming point reference other than the waterline itself.
- This report is the unvarnished truth, no playing with the numbers nor cherry picking.
The target is below. It has two water lines – 10-shots each. I tested two different lot#s. The top waterline (waterline 1 - W1) was shot with the last box of that lot. This lot was slower than previous lots as well as the newer lot that was shot below it (waterline 2 - W2). I shot 5 shots at a time with a barrel cooling period in between those strings.... The distance to target is exactly 106 yards. It pays to know that for accuracy on the ballistics app. There was no wind to speak of.
Both W1 and W2 were shot with the tuner installed and the setting was not changed for the shots on the waterlines.
There are also 3-round targets on the paper. The top target was used to warm up the rifle.
So then, I shot W1 and W2 and recorded the velocities. The new lot# on W2 was faster with velocities and ES more in tune with what I get with this rifle/ammo combo, which is higher 2700s with some rounds almost kissing 7800 fps. The results between W1 and W2 are clear as day. On W1 the barrel was in a max nosedive at 2757 FPS - the last shot, which also happened to be the slowest in W1.
When done, I removed the chrono and shot 5 shots with each lot# at the two remaining round targets, each of those under their corresponding waterline. And this is where it gets interesting.
By looking at the velocities of the Lot on W1 and according to Tim, I needed to adjust the tuner back towards the action, so I did – a 1/8 of a turn. The results on the target were as Tim predicted.
For the target below W2 and the new lot# I shot 5 shots at it BUT, I brought the tuner back to its original setting! Why? Because W2 showed that I need to move the tuner further out (not much) from its original setting and instead of doing that I wanted to see the actual vertical dispersion. So, I turned it back out to the original setting
Note: That target for W2 shows an errant shot to the left, went there because as I was pressing the trigger the CEASE FIRE! CEASE FIRE! call was sounded and I pushed the last shot.
The vertical dispersion on the W2 target is textbook, the kind that tuners were made for. Furthermore I can now tell that the next time out I will start by moving the tuner OUT 1/16 of a turn or less from the original position. Notice that all shots trend higher.
Thanks again Tim!
Velocities:
W1:
| Series | 2 | Shots: | 10 |
| Min | 2757 | Max | 2789 |
| Avg | 2768 | S-D | 10.6 |
| ES | 32 | ||
| Series | Shot | Speed | |
2 | 1 | 2768 | ft/s |
2 | 2 | 2773 | ft/s |
2 | 3 | 2781 | ft/s |
2 | 4 | 2789 | ft/s |
2 | 5 | 2774 | ft/s |
2 | 6 | 2765 | ft/s |
2 | 7 | 2760 | ft/s |
2 | 8 | 2760 | ft/s |
2 | 9 | 2758 | ft/s |
2 | 10 | 2757 | ft/s |
W2:
| Series | 3 | Shots: | 10 |
| Min | 2770 | Max | 2796 |
| Avg | 2779 | S-D | 7.8 |
| ES | 26 | ||
| Series | Shot | Speed | |
3 | 1 | 2773 | ft/s |
3 | 2 | 2796 | ft/s |
3 | 3 | 2776 | ft/s |
3 | 4 | 2776 | ft/s |
3 | 5 | 2776 | ft/s |
3 | 6 | 2776 | ft/s |
3 | 7 | 2781 | ft/s |
3 | 8 | 2777 | ft/s |
3 | 9 | 2789 | ft/s |
3 | 10 | 2770 | ft/s |
Last edited:
Here we go Tim….
I have as couple of caveats before I go on though:
Now to the details. I shot this with my 6mm ARC bolt gun. It's running on a Defiance action, and the barrel is 26-inches in an MTU contour. I’m running factory ammunition with Hornady 108 ELDs You can see it here:
- This was a small test.
- That’s kind of a good thing in a way because I was still able to see cause and effect and thus the test saves ammunition.
- You will see the target below had aiming points on the water lines. That went out the window. I had trouble seeing them. even at 27X because we had a low, dark overcast moving from west to east with very brief lighter conditions where I could see them.
- So, Azimuth was all over the place because most of the time I had no aiming point reference other than the waterline itself.
- This report is the unvarnished truth, no playing with the numbers nor cherry picking.
The target is below. It has two water lines – 10-shots each. I tested two different lot#s. The top waterline (waterline 1 - W1) was shot with the last box of that lot. This lot was slower than previous lots as well as the newer lot that was shot below it (waterline 2 - W2). I shot 5 shots at a time with a barrel cooling period in between those strings.... The distance to target is exactly 106 yards. It pays to know that for accuracy on the ballistics app. There was no wind to speak of.
Both W1 and W2 were shot with the tuner installed and the setting was not changed for the shots on the waterlines.
There are also 3-round targets on the paper. The top target was used to warm up the rifle.
So then, I shot W1 and W2 and recorded the velocities. The new lot# on W2 was faster with velocities and ES more in tune with what I get with this rifle/ammo combo, which is higher 2700s with some rounds almost kissing 7800 fps. The results between W1 and W2 are clear as day. On W1 the barrel was in a max nosedive at 2757 FPS - the last shot.
When done, I removed the chrono and shot 5 shots with each lot# at the two remaining round targets, each of those under their corresponding waterline. And this is where it gets interesting.
By looking at the velocities of the Lot on W1 and according to Tim, I needed to adjust the tuner back towards the action, so I did – a 1/8 of a turn. The results on the target were as Tim predicted.
For the target below W2 and the new lot# I shot 5 shots at it BUT, I brought the tuner back to its original setting! Why? Because W2 showed that I need to move the tuner further out (not much) from its original setting and instead of doing that I wanted to see the actual vertical dispersion. So, I turned it back out to the original setting
Note: That target for W2 shows an errant shot to the left, went there because as I was pressing the trigger the CEASE FIRE! CEASE FIRE! call was sounded and I pushed the last shot.
The vertical dispersion on the W2 target is textbook, the kind that tuners were made for. Furthermore I can now tell that the next time out I will start by moving the tuner OUT 1/16 of a turn or less from the original position. Notice that all shots trend higher.
Thanks again Tim!
Velocities:
W1:
Series Shots: Min Max Avg S-D ES Series Shot Speed ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s
W2:
Series Shots: Min Max Avg S-D ES Series Shot Speed ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s
Thanks for sharing.
This would be an interesting follow-up:
- shoot this same test over multiple days and conditions
- shoot a waterline test as well with no adjustments, as a control
It would be interesting to see if 1. The test is repeatable and 2. How much variation a straight up waterline with no tuner adjustments shows
Here we go Tim….
I have as couple of caveats before I go on though:
Now to the details. I shot this with my 6mm ARC bolt gun. It's running on a Defiance action, and the barrel is 26-inches in an MTU contour. I’m running factory ammunition with Hornady 108 ELDs You can see it here:
- This was a small test.
- That’s kind of a good thing in a way because I was still able to see cause and effect and thus the test saves ammunition.
- You will see the target below had aiming points on the water lines. That went out the window. I had trouble seeing them. even at 27X because we had a low, dark overcast moving from west to east with very brief lighter conditions where I could see them.
- So, Azimuth was all over the place because most of the time I had no aiming point reference other than the waterline itself.
- This report is the unvarnished truth, no playing with the numbers nor cherry picking.
The target is below. It has two water lines – 10-shots each. I tested two different lot#s. The top waterline (waterline 1 - W1) was shot with the last box of that lot. This lot was slower than previous lots as well as the newer lot that was shot below it (waterline 2 - W2). I shot 5 shots at a time with a barrel cooling period in between those strings.... The distance to target is exactly 106 yards. It pays to know that for accuracy on the ballistics app. There was no wind to speak of.
Both W1 and W2 were shot with the tuner installed and the setting was not changed for the shots on the waterlines.
There are also 3-round targets on the paper. The top target was used to warm up the rifle.
So then, I shot W1 and W2 and recorded the velocities. The new lot# on W2 was faster with velocities and ES more in tune with what I get with this rifle/ammo combo, which is higher 2700s with some rounds almost kissing 7800 fps. The results between W1 and W2 are clear as day. On W1 the barrel was in a max nosedive at 2757 FPS - the last shot, which also happened to be the slowest in W1.
When done, I removed the chrono and shot 5 shots with each lot# at the two remaining round targets, each of those under their corresponding waterline. And this is where it gets interesting.
By looking at the velocities of the Lot on W1 and according to Tim, I needed to adjust the tuner back towards the action, so I did – a 1/8 of a turn. The results on the target were as Tim predicted.
For the target below W2 and the new lot# I shot 5 shots at it BUT, I brought the tuner back to its original setting! Why? Because W2 showed that I need to move the tuner further out (not much) from its original setting and instead of doing that I wanted to see the actual vertical dispersion. So, I turned it back out to the original setting
Note: That target for W2 shows an errant shot to the left, went there because as I was pressing the trigger the CEASE FIRE! CEASE FIRE! call was sounded and I pushed the last shot.
The vertical dispersion on the W2 target is textbook, the kind that tuners were made for. Furthermore I can now tell that the next time out I will start by moving the tuner OUT 1/16 of a turn or less from the original position. Notice that all shots trend higher.
Thanks again Tim!
Velocities:
W1:
Series Shots: Min Max Avg S-D ES Series Shot Speed ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s
W2:
Series Shots: Min Max Avg S-D ES Series Shot Speed ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s ft/s
Okay I just spent some time re-reading this.
Is there supposed to be a correlation between the waterline tests and the velocities plotted for each shot? I personally don't see any meaningful way to interpret the waterline shots when compared to their velocity. I see that there is a conclusion being made in regards to the 2757 fps shot on W1, but honestly there isn't enough data to make such a dispositive conclusion.
Maybe there's something to it. I think it would be interesting to see this test performed multiple times over multiple days, to see what correlations are repeatable. 1 or 2 shots per MV is just not enough data to interpret any trends. There's also a lot of other variables in play besides just MV that aren't being controlled.
The data is intriguing - especially if its consistently repeatable. But nothing here is conclusive or convincing. Also I'm not sure what exactly the 3 groups are telling us here.
To establish on my point - look at W2.
There are four shots of 2776 fps in a row. Look at the variance in amplitude of each shot from those four shots. Exact same MV's, but relative to the entire test there's a big dispersion in the Y-axis.
That alone just goes to show that you can't really make any real conclusions in regards to amplitude in relation to MV. There's variables beyond MV that are not being controlled and causing amplitude deflection, so there's no reasonable way anyone can interpret that waterline test in regards to those two variables (MV versus amplitude to WL).
There are four shots of 2776 fps in a row. Look at the variance in amplitude of each shot from those four shots. Exact same MV's, but relative to the entire test there's a big dispersion in the Y-axis.
That alone just goes to show that you can't really make any real conclusions in regards to amplitude in relation to MV. There's variables beyond MV that are not being controlled and causing amplitude deflection, so there's no reasonable way anyone can interpret that waterline test in regards to those two variables (MV versus amplitude to WL).
Kthomas
The easiest test for most shooters is to develop your most accurate load possible then add a 8 ounce tuner to the barrel and shoot that same ammo while making extremely small changes to the tuner itself.
If you like the results keep using the tuner if you don't sell it online.
The easiest test for most shooters is to develop your most accurate load possible then add a 8 ounce tuner to the barrel and shoot that same ammo while making extremely small changes to the tuner itself.
If you like the results keep using the tuner if you don't sell it online.
That's all fine and dandy.
But it's imperative for people to understand proper testing protocols, controlling and isolating variables, understanding test limitations and ultimately understanding what conclusions you can and can't draw from any given "test".
Generally speaking, our community of shooters has a very poor understanding of the above. It's not just with tuners, but reloading in general. Way too often people draw conclusions from tests that are way too limited to do so.
The above test is a clear example of that (and no offense is meant to the shooter in that specific example).
I find that most engineers over analyze everything and most shooters just do what works on the target.
I proposed a test you can do then tell us if it worked or didn't work.
It's fun to bench race and argue theories but it's even more fun just to do it and draw your own conclusions
I proposed a test you can do then tell us if it worked or didn't work.
It's fun to bench race and argue theories but it's even more fun just to do it and draw your own conclusions
Just pointed out the flaws of the test conducted above, and how you can't really draw any conclusions from it.
Post #41 clearly points out the limitations of the test and how its flawed to draw any conclusions from it.
Well picture the barrel as a sine wave. Now add weight to the muzzle and that sine waves amplitude will decrease.
The now more flattened out area will shoot with less vertical
Can you picture that happening?
The now more flattened out area will shoot with less vertical
Can you picture that happening?
Sure.
But the test @JAS-SH did doesn't show that. The test is way to limited in scope and control of variables (or lack thereof) to draw any such conclusions.
Let's take this in small steps in the hopes it helps others.
If you have a piece of welding rod or a fishing pole and you shake it up and down it produces a standing wave. Which just means everything looks the same along its length.
A gun barrel does the same thing it's just very small and the human eye doesn't see it. A cantilevered beam if we might.
Now back from the muzzle or back from the front guide or back from the tip of the welding rod we will see a point that looks still called a node.
Are we good so far?
If you have a piece of welding rod or a fishing pole and you shake it up and down it produces a standing wave. Which just means everything looks the same along its length.
A gun barrel does the same thing it's just very small and the human eye doesn't see it. A cantilevered beam if we might.
Now back from the muzzle or back from the front guide or back from the tip of the welding rod we will see a point that looks still called a node.
Are we good so far?
I completely understand that.
The test that was shown does not have the ability to conclude that the barrel is in any position of amplitude per MV.
Let's not worry about what has been posted as Tim can explain thar let's just keep going.
If we take a barrel blank and hang the chamber end from a string letting the muzzle point to the ground we can ring the barrel with a small wrench hammer or screwdriver and listen to it vibrate.
We can then take a finger or 2 and run it along the muzzle looking for that node we can see in both the welding rod or the fishing pole.
It will feel like nothing is vibrating while we can feel the barrel vibrating on both sides of that point.
We can mark that point with a sharpie and do the test multiple times to confirm it is there.
For the average barrel we would see in this forum that node would be roughly 2.5-3 inches back from the muzzle.
To the average shooter it would resemble a teeter tottering.
Are we still good?
If we take a barrel blank and hang the chamber end from a string letting the muzzle point to the ground we can ring the barrel with a small wrench hammer or screwdriver and listen to it vibrate.
We can then take a finger or 2 and run it along the muzzle looking for that node we can see in both the welding rod or the fishing pole.
It will feel like nothing is vibrating while we can feel the barrel vibrating on both sides of that point.
We can mark that point with a sharpie and do the test multiple times to confirm it is there.
For the average barrel we would see in this forum that node would be roughly 2.5-3 inches back from the muzzle.
To the average shooter it would resemble a teeter tottering.
Are we still good?
