What is your holdover at 75 Chairgun says 1.41 if that's not what you're coming up with your input is wrong
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Pellet speed H&N 5.5mm
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One minor point, don't take anything you see in YouTube videos as being correct. In the Ted's Holdover video if you look at the picture of his input data to calculate BC you will see he has the temperature as zero degrees F, yet he is walking around in shorts and a tea shirt and all the trees have their leaves. This is probably the main reason for his high BC, as the calculator would have worked using an air density way above reality and the calculated Mach number would also have been too high.Follow up.
I am playing with different things to see what it does to accuracy. I saw Gary Chillingworth on Shooting & Country TV channel have a bunch of weights on his one AA springer rifle to improve accuracy, so he says.
I put a piece of leather between my rifle's barrel shroud and the air tube and then tightly taped a bunch of mag wheel weights to it. I had to re-zero the rifle at 50 meter. Then adjusted 3.5 MRad up as always to shoot at the 100 meter target. The pellet missed the plate low. I then adjusted higher and higher to be about on target. The turret setting ended at 4.2 MRad to be close to POA, closer to the setting given by Strelok with the BC given by H&N. However, I still had to adjust the BC in Strelok to about .038, not precise. It is also known that a projectile's BC alters with speed, so I still don't know what the correct value must be.
As well as what Matt showed about JSB pellets in his video previously linked in the thread.
2.4 Lessons Learned from Ballistic Coefficient Testing - Sierra Bullets
www.sierrabullets.com
Ted from the channel Teds HoldOver also found different POI with increase of speed with his FX and slugs. He also at first concluded that the BC increased but in the comments and elsewhere here on AGN is was concluded that it was barrel harmonics causing the different POI and not the BC per se. I don't know what Ted's final conclusion was after the video and comments. Video below.
My conclusion is that it happens because the barrel is now stiff with all the weight and tape and don't move as much causing it to have a different POI. Without the weights the 3.5 MRad setting can only be because of barrel harmonics causing the pellet to shoot higher than what Strelok is calculating and I had to compensate on the turrets for it by dialing less MRad upwards.
The problems with the extra weigh is that the group open up a lot and that the rifle is now heavier and uncomfortable to carry in the field if I want to. So, knowing this I removed the weights and leather again. The leather was to prevent the tape to close the gap between barrel and tube. The thing is that I don't know if there is a way to compensate for it in Strelok other than adjusting the BC as I did before.
Another question, will a barrel tuner correct the harmonics to:
(1) Bring the dial setting to what it must be?
and /or
(2) Will a barrel tuner improve accuracy?
Both that questions I can only know the answer to if I buy and install a barrel tuner and test it. I did see it improving accuracy on a FX in a video as below from Airbuks
Video from Teds HoldOver:
Video from Airbuks:
As for Matt Dubbers videos, because he appears to know very little about ballistics or aerodynamics, the videos on pellet flight or stability contain a large number of mistakes. The worst one was his explanation of pellet aerodynamic stability, which was quite frankly rubbish and one of the reasons I produced a series of threads on pellet stability to try to get the facts out to shooters.
G1 is not a suitable reference drag law for pellets. Ga and GA2 were developed specifically for diabolo pellets. Using G1 gives low BC values at high speeds, as the reference drag law increases more slowly with Mach number compared to diabolo pellets. For slugs, it is the opposite way round, using the G1 drag law gives high BC values at high speeds as the slug drag increases less with increasing speed until a critical Mach number is reached. For slugs, use SLG0 or RA4 reference drag laws, unless they have a boat tail where SLG1 may be better.
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As I say above, both GA and GA2 are specifically for round nose diabolo pellets. WC0 is for wadcutter diabolo pellets.
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Anyone who uses G1 for pellets does not have "knowledge" of external ballistics. I know H&N and many other European pellet makers use G1, but it does not mean it is correct. One look at the reference G1 projectile shape compared to a pellet shape should tell you that. The clue lies in the BC values themselves, if they change significantly with speed, the reference drag law is wrong. But in the end, it all depends on how accurate you want to be in your calculations. External ballistic knowledge within the small arms industry in general has been a problem for many years. It is only relatively recently that the subject has been taken more seriously within the industry.
You do not have to "buy" any apps for access to GA, GA2 or any of the other reference drag laws I mentioned. They are all available in free ballistic apps, most notably MERO which was developed specifically for airgun use.
I understand that Matt Dubber is not a trained expert in aerodynamics or ballistics, but he is putting videos on the internet which purport to explain aerodynamic and ballistic phenomena. They are full of mistakes, and he is apparently not interested in correcting those mistakes. The internet in general is not a good source of information on projectile aerodynamics and ballistics, as it is too specialized a subject. The articles on Wikipedia also contain mistakes. Finding good source material can be difficult as a lot of it is classified for obvious reasons. I worked for 40 years exclusively on gun and rocket projectile external ballistic research, design and testing in a BRL equivalent organization, which is why I had access to all the sources and training.
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I do not use any app . i take my gun and shoot at a known distance if my poi is off i shoot 2 more shots . if the poi is the same i reset my sights to that poi and shoot again , Ahhh on target . Easy .
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I had nothing to do with its development or the software that was done by the late George Conway. All I have ever done is provide some suggested drag laws, but again I have had no input into the GA drag law, that was in the original Chairgun. The original developer of Chairgun now looks after the MERO software since its original developer sadly passed away late last year.I see it is a app you developed, so that is why you promote it.
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to each his own i guess , I wasn't putting this type of shooting down, i just prefer Knowing just what my gun and I are capable of .
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There used to be an email address on the GPC website where you could ask questions and George would either explain how to do it if possible or incorporate changes into future versions of the software. I am not sure if the email is still there since George passed away.In the MERO app, a few things I see.
* If I change the far zero, the killzone size automatically change to something else than my input. If I then change the killzone input, the far zero change so something else than my input.
* Is there a way to have MRad per click instead of MoA per click?
Maybe there is a few other things I will struggle with as well.
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I can't remember right off top but something I picked up from a pioneer in airguns and airgun building world.he said the first thing he does is make sure your turrets are zeroed in both directions and would shoot a group and if the poi was off more than just a few clicks could compensate for he would take the liner and would bend and bring the poi to be close to the POA while the scope was a mechanical zero and would go from there .it sounds crazy at first but it makes all the difference.now keep in mind when I say bend it's more like massage the liner in the right directionFollow up.
I am playing with different things to see what it does to accuracy. I saw Gary Chillingworth on Shooting & Country TV channel have a bunch of weights on his one AA springer rifle to improve accuracy, so he says.
I put a piece of leather between my rifle's barrel shroud and the air tube and then tightly taped a bunch of mag wheel weights to it. I had to re-zero the rifle at 50 meter. Then adjusted 3.5 MRad up as always to shoot at the 100 meter target. The pellet missed the plate low. I then adjusted higher and higher to be about on target. The turret setting ended at 4.2 MRad to be close to POA, closer to the setting given by Strelok with the BC given by H&N. However, I still had to adjust the BC in Strelok to about .038, not precise. It is also known that a projectile's BC alters with speed, so I still don't know what the correct value must be.
As well as what Matt showed about JSB pellets in his video previously linked in the thread.2.4 Lessons Learned from Ballistic Coefficient Testing - Sierra Bullets
Ted from the channel Teds HoldOver also found different POI with increase of speed with his FX and slugs. He also at first concluded that the BC increased but in the comments and elsewhere here on AGN is was concluded that it was barrel harmonics causing the different POI and not the BC per se. I don't know what Ted's final conclusion was after the video and comments. Video below.
My conclusion is that it happens because the barrel is now stiff with all the weight and tape and don't move as much causing it to have a different POI. Without the weights the 3.5 MRad setting can only be because of barrel harmonics causing the pellet to shoot higher than what Strelok is calculating and I had to compensate on the turrets for it by dialing less MRad upwards.
The problems with the extra weigh is that the group open up a lot and that the rifle is now heavier and uncomfortable to carry in the field if I want to. So, knowing this I removed the weights and leather again. The leather was to prevent the tape to close the gap between barrel and tube. The thing is that I don't know if there is a way to compensate for it in Strelok other than adjusting the BC as I did before.
Another question, will a barrel tuner correct the harmonics to:
(1) Bring the dial setting to what it must be?
and /or
(2) Will a barrel tuner improve accuracy?
Both that questions I can only know the answer to if I buy and install a barrel tuner and test it. I did see it improving accuracy on a FX in a video as below from Airbuks
Video from Teds HoldOver:
Video from Airbuks:
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I have uploaded the MERO app and it's pretty good. Of course not the same as Strelok, takes a little getting used to it, but pretty good overall.
Comparing it to Strelok, I noted yesterday that a 126 yard shot showed 5.1 MIL (51 clicks). This was incorrect as I missed my target low. I found a small, .5" pebble to shoot at that range and found that it should have been 5.4 (I ultimately got my target at that setting).
MERO spit out 5.4 MIL, so spot on, after checking that everything was identically input. I like it, although it does show MOA, all of the information for MOA and MIL are within the Target Distance Box, so no biggie.
Thanks BB for the information!
Mike
Comparing it to Strelok, I noted yesterday that a 126 yard shot showed 5.1 MIL (51 clicks). This was incorrect as I missed my target low. I found a small, .5" pebble to shoot at that range and found that it should have been 5.4 (I ultimately got my target at that setting).
MERO spit out 5.4 MIL, so spot on, after checking that everything was identically input. I like it, although it does show MOA, all of the information for MOA and MIL are within the Target Distance Box, so no biggie.
Thanks BB for the information!
Mike
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Nice video about an interesting guy.
About 2 years ago I did bend the barrel on my Gamo Magnum as the POI was to the left and I had to adjust a lot on the open sights to get it to zero. It then helped with zeroing the scope without to much adjustment as well. I want both the open sights and the scope to be more or less zeroed for if something goes wrong with the scope that I can still use open sights.
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I think you're doing great already!
I am on the same journey as you — trying to get Strelok to line up with non-conventional pellets, and non-conventional velocities and ranges:
E.g.: shooting hollow points (that don't fit any of the current drag profiles) — at velocities over 900fps (where the certainly will have a different drag coefficient than the dome that the GA model uses as their base projectile.
I am only a few weeks away from trying what I will suggest to you here:
If you can, measure the velocities with a chrony at several different ranges (10-15 shot averages), especially where the projectile is flying at high velocities close to you, maybe: 0m — 15m — 30m — 60m — 100m. Measuring actual velocities is more precise than measuring projectile drop (because the barrel oscillations [barrel harmonics] can falsify true drop values). But better drop than nothing. 
Then, using trial and error, enter variable BC numbers into Strelok until the Strelok values match up what you measured in your tests (velocity, or drop). Instead of 5 variable BC numbers, Strelok also allows you to enter a custom drag model that allows for finer adjustments.
Let's see what Ballisticboy says — what a privilege to have him here at AGN.
Cheers,
Matthias
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● You won't need a radar chrony. So far I have been using a simple Caldwell ballistics chrono.
Buying one with a light kit is worth the extra cash. At night there is less wind in my coastal desert corner of the globe.
Similar types: ▪Competition Electronics Pro | ▪Shooting Chrony
● Put a thick acrylic glass before the breakable sections of the chrony, because a chrony-cide is unlawful.
● Measure the distances several times to make sure they're correct.
● Make sure you keep the pressure in your gun within the range where you have the least variation in muzzle velocities.
● Do record the meteorological conditions, and use for your calculations.
I'm just repeating what I have learned on the forums....
Great place to learn.
Matthias
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Using trajectory validation:
On the main screen with the 8 buttons on the bottom ➔ bottom row ➔ far right button (with target and double arrow).
On the trajectory validation screen you select BC, and enter your MV, and the drop at a distance far, far beyond your zero range.
Strelok will give you a single BC number, using the drag model you selected when setting up your "bullet".
However, you observe that your particular pellet does not seem to follow the standard drag model of GA — especially at high velocities.
➔ So, this trajectory validation only works to the range that you "validated" the trajectory, other ranges will be off as you have observed.
➠ So, it seems like you're on for shooting groups at different ranges, and then tweaking Strelok, either adapting via trial and error 5 custom BC values, or a full custom drag model.
I think it can be done. (But don't be fooled by my confidence, I'm pretty ignorant.
➔ Miles/ Ballisticboy is the man. ) Matthias
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It sounds to me as if the pellet in question has a steeper drag rise than the GA profile, which would seem correct looking at the pellet pictures shown in the thread. It is possible that the wadcutter drag profile may fit it better, though that one might be too steep a drag rise.
A purpose drag law could be created from the BC values at the different ranges by getting the form factors and thus the drag coefficient but, it is a fairly long-drawn-out process and needs a bit of imagination as to what is likely or unlikely. There is also the danger that the calculated values are based on measured drop which is the least accurate method, the reason being that there are a number of other things which can effect drop. The most accurate method with one chrono is by measuring MV and time of flight, possibly with one microphone and a laptop, though it would be difficult at the long ranges. Even with the time of flight and the MV, it may still be difficult if the reference drag laws are not the correct shape.
A purpose drag law could be created from the BC values at the different ranges by getting the form factors and thus the drag coefficient but, it is a fairly long-drawn-out process and needs a bit of imagination as to what is likely or unlikely. There is also the danger that the calculated values are based on measured drop which is the least accurate method, the reason being that there are a number of other things which can effect drop. The most accurate method with one chrono is by measuring MV and time of flight, possibly with one microphone and a laptop, though it would be difficult at the long ranges. Even with the time of flight and the MV, it may still be difficult if the reference drag laws are not the correct shape.
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The Rifle Premium Round weigh 18.67gr. They state a 0.025BC.
Comparing your actual photo of the Rifle Round with the following... — might that be the same pellet — rebranded?
The Crosman Domed Ultra Heavy weigh 19.00gr.
The BCs that were measured by different shooters were mostly disappointingly low for such a heavy pellet:
▪ 0.017BC | MV 898fps | Range 30y
(by HAM)
▪ 0.021BC | MV 860fps | Range 5–83y
▪ 0.031BC | MV 750fps to 650fps | Range 25y
(Note: All these were calculated using ChairGun and GA.)
This pellet seems to behave more like a wadcutter than a dome....: The higher the velocity, the higher the drag (or, the lower the "apparent BC").
Maybe that's why you see such a weird trajectory — the GA standard projectile does not work for this shape at higher velocities....
Matthias
Comparing your actual photo of the Rifle Round with the following... — might that be the same pellet — rebranded?
The Crosman Domed Ultra Heavy weigh 19.00gr.
The BCs that were measured by different shooters were mostly disappointingly low for such a heavy pellet:
▪ 0.017BC | MV 898fps | Range 30y
(by HAM)
▪ 0.021BC | MV 860fps | Range 5–83y
▪ 0.031BC | MV 750fps to 650fps | Range 25y
(Note: All these were calculated using ChairGun and GA.)
This pellet seems to behave more like a wadcutter than a dome....: The higher the velocity, the higher the drag (or, the lower the "apparent BC").
Maybe that's why you see such a weird trajectory — the GA standard projectile does not work for this shape at higher velocities....
Matthias
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