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Pellet speed H&N 5.5mm

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JungleShooter said:
OK, this is intriguing.

I replicated your Strelok Pro data — AND they match!:
I got 4.6mil up (with 0.029BC) — you got pretty much the same (4.47mil).


BUT your shots are HIGH at your 100m steel target:
They are (eyeballing the group) about 2.5cm high = 2.5mil
PLUS you dialed only 3.5mil (=3.5cm) instead of 4.5mil.
➠ So, your group is really 3.5mil (= 3.5cm = 1.4") too high.

It's not off-the-chart high, but for level of precision (you shot an awesome group!!) — way too high.


So, here are some other things to check or test to see if they fix this error.


➊ Does your scope touch the barrel/shroud at all?
Just yesterday I installed that same scope model on a picatinny rail with low mounts, and could not squeeze a piece of paper between rail and objetive bell. Definitely a no-no, I had to change the rings for something a bit higher.
Fortunately, I didn't tighten down the rings, otherwise, I might have bent the scope tube.... 😱


➋ Do you have a barrel band installed? Or do your airtube and the shroud touch each other at some point?
If that is the case, next uestion: Do you possibly "load the bipod" when shooting (or otherwise make the gun press downward into the shooting bags or bipod)?
➠ Then, the barrel might get bent up just a fraction of a milimeter, and shoot high.


➌ Some might say that the scope you (and I) are using to dial our elevation is not expensive enough to do that reliably.
In other words, when you turn the elevation turret 5.0 mils up, the reticle does not consistently[i/] move up 5 mils, but less, or more.
You can test that (some YouTube instructionals out there), and Strelok allows you to enter a corrected click value (GPC has a turret click validator app).


Cheers,

Matthias 😊
Click to expand...
First I should have said that I aimed for the top left cross. That put the shots about on the right elevation. Sorry, my mistake.

"➊ Does your scope touch the barrel/shroud at all?" No, the scope cleat the barrel shroud with 4mm and the slip-on lens cover clear with 1mm.

"➋ Do you have a barrel band installed? ..... " Yes, the rifle comes with a barrel band. The barrel shroud and air tube does not touch and the shroud does have some free play in the barrel band. I am using shooting bags. No, I don't press down on it, I just hold on top of the scope to stabilise it. I hold light cheek and shoulder pressure as well. I tried more pressure everywhere, together and singular, but that makes my shots inconsistent. It however does not cause the shots to be high, just all over the target, high, low, left and right.

"➌ Some might say that the scope you (and I) are using ...... " All my other scopes are Hawke. I had a Hawke Airmax 4-12x40 AO on this rifle and the amount I had to dial was the same as this Discovery. If that say something. Even my BP rifles from .22LR, .308 and .50 muzzle loader has Hawke scopes on it and I did not experience dial problems with that. But, I will do that test, sometime.


Thanks for the reply.
 
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You did what?! 😆
You did NOT aim for the center bull's eye, but for the left top X?! 😆

352588219.jpg




OK, in that case, well... — your shots are 1.0mil (10cm = 4") too high —
as you dialed 3.5mil up instead of the 4.5mil that Strelok suggested using reasonable data (the 0.029 BC for the Baracuda 18 is very reasonable).
1.0mil — 10cm — 4" is a lot at 100m (considering your very small group)....


Even if your chrony misread your MV and instead of 940fps you were shooting that pellet at 1050fps — Strelok would still tell you to compensate 3.9mil at 100m, which results in shooting 4cm too high.


You'd need a tail wind of 60km/h (36mph) in order to get the 4.5mil compensation Strelok suggested down to the 3.5mil which would put your shots where you aimed them.


It's a mystery.... 🤔

Matthias
 
Last edited:
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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.

www.sierrabullets.com

2.4 Lessons Learned from Ballistic Coefficient Testing - Sierra Bullets

www.sierrabullets.com www.sierrabullets.com
As well as what Matt showed about JSB pellets in his video previously linked in the thread.

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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Otherwise, most of the time it is pushing all 5 pellets through one hole at 25 meter.

This afternoon when shooting at 75 meter, it was grouping about 20-30mm. I did not walk down to measure, that was just using the reticle to estimate. There is something happening between 75 meter and 100 meter causing the pellets to open. I was thinking if the higher spin rate at the lower speed at distance has something to do with it? But then it will do so with other rifles as well. Some say their rifles shoots 18gr pellets at 1 moa at that distance. Maybe a slower twist rate barrel?
 
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Strelok say -0.7 mrad. I cannot remember where I put it for 25m. Will check when I shoot again. The difference between .5 and .7 at 25 is only about 5mm.

I don't know how the different apps compare to each other but in my opinion a app is just to get you in the ballpark untill you get all the dope correctly entered. Strelok does not have a function to compensate for things like barrel harmonics which will be a good thing. I think, in fact, I am sure this is the influencing factor here.
 
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Klaas said:
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.

www.sierrabullets.com

2.4 Lessons Learned from Ballistic Coefficient Testing - Sierra Bullets

www.sierrabullets.com www.sierrabullets.com
As well as what Matt showed about JSB pellets in his video previously linked in the thread.

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:

Click to expand...
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.

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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Ballisticboy said:
don't take anything you see in YouTube videos as being correct
Click to expand...
I never do. That is why I said about Gary Chillingworth "so he says". About Matt, he did say in one of the videos that he is not an expert on the subject and it is about what he researched. So, I take all info on the internet as something to do further investigation to evaluate by myself what is correct or not. Including what I read here on AGN what others like you say. I do that from a very young age, long before the internet existed, to this day. Only the real Gospel is gospel.

As for what model to use, many people with knowledge differ. I understand that H&N is using the G1 model when determining the BC of their pellets. I don't know about JSB. Like I said in post #8 in this thread:
Klaas said:
I saw that the difference between G1, RA4 and GA is almost non-existent in this calculation.
Click to expand...
Strelok does not show a GA2 model. I don't know how all the different models works but what I do know is that I see a lot of people argue back and forth about what is correct for what projectiles. The same with the different apps available. I use Strelok because that is what I have and I am not going to buy all the different apps just to compare.
 
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Klaas said:
As for what model to use, many people with knowledge differ. I understand that H&N is using the G1 model when determining the BC of their pellets. I don't know about JSB. Like I said in post #8 in this thread:

Strelok does not show a GA2 model. I don't know how all the different models works but what I do know is that I see a lot of people argue back and forth about what is correct for what projectiles. The same with the different apps available. I use Strelok because that is what I have and I am not going to buy all the different apps just to compare.
Click to expand...
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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Ballisticboy said:
he is apparently not interested in correcting those mistakes
Click to expand...
Very few people are willing to take down a video as those videos assure an income to them. Nor are they willing to re-do and re-post such videos as it is a lot of work they don't want to do. In fact, many will knowingly and deliberately lie just to get views.
Ballisticboy said:
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.
Click to expand...
Good to know this. It is sometimes difficult to distinguish between a person worth listening to and little "Joe" sitting in his mom's basement doing copy and past posts or videos. On RCGroups there was this one guy everybody turned to for knowledge. For years he gave help and information to everybody asking about model aeroplanes, RC equipment, engines, electric motors etc.- etc. After many years people found out that he never owned or handled any of those items and all he knew was what he read and many times just copied information and gave it in his own words.
 
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