GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: rsterne on July 20, 2017, 12:53:22 AM
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I ran across this tonight, and it appears to be a fabulous resource.... http://www.accurateshooter.com/ballistics/bullet-database-with-2900-projectiles/ (http://www.accurateshooter.com/ballistics/bullet-database-with-2900-projectiles/)
It has over 3900 bullets, including many cast bullets.... You can access the data by caliber, and sort by manufacturer, weight, length, or other factors.... It gives the Sectional Density (SD), and the Ballistics Coefficient (I assume G1) at different velocities (if known).... As an example, here are the results for the popular Lyman 257420....
SD = 0.148
BC above 2200 fps = 0.129
BC above 1800 fps = 0.152
BC above 1300 fps = 0.18
BC above 800 fps = 0.20
BC below 800 fps = 0.15
I have only just begun to explore this database, but wanted to share it with all of you....
Bob
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Very nice! Thanks for the tip Mr Bob!!
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Awesome stuff Bob. I need to spend some time on that site in general.
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I ran across this tonight, and it appears to be a fabulous resource.... http://www.accurateshooter.com/ballistics/bullet-database-with-2900-projectiles/ (http://www.accurateshooter.com/ballistics/bullet-database-with-2900-projectiles/)
It has over 3900 bullets, including many cast bullets.... You can access the data by caliber, and sort by manufacturer, weight, length, or other factors.... It gives the Sectional Density (SD), and the Ballistics Coefficient (I assume G1) at different velocities (if known).... As an example, here are the results for the popular Lyman 257420....
SD = 0.148
BC above 2200 fps = 0.129
BC above 1800 fps = 0.152
BC above 1300 fps = 0.18
BC above 800 fps = 0.20
BC below 800 fps = 0.15
I have only just begun to explore this database, but wanted to share it with all of you....
Bob
I was just looking for this precise information! Awesome, thanks Bob!
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Here is the one Strelok uses.... http://www.shootforum.com/forum/bulletdb.html (http://www.shootforum.com/forum/bulletdb.html)
It is the same one, just a direct link.... It is certainly a good one, and user friendly, with lots of cast bullets shown.... Unfortunately, they don't have NOE bullets in the list.... :(
Bob
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Here is the one Strelok uses.... http://www.shootforum.com/forum/bulletdb.html (http://www.shootforum.com/forum/bulletdb.html)
It is the same one, just a direct link.... It is certainly a good one, and user friendly, with lots of cast bullets shown.... Unfortunately, they don't have NOE bullets in the list.... :(
Bob
Thanks Bob. Strelock might be a game changer for me. I'm furiously studying it, and changing variables to see the effect. Up to now I've just been winging it. But if Strelock is close to being accurate in it's predictions then I am one happy and excited camper. I guess I'm just a slow learner to have not embraced this before.
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Just be aware, if there is not speed numbers in all the columns it looks like the values are all the same. Which for the 225438 and 225462 I am having a little bit of trouble reconciling as anything but a single SS number. The 462 should have a significantly higher 'over 800' number than the 438...and for the 225107, the numbers stop at 1800 fps...with no rise in the 'over 800' column. Now the 225415 shows them all, and is a very fine performer for a 50 gr boolit. This is the newer, revised 22596 profile I believe...:)
cheers,
Douglas
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I just bough a tablet and Strelok Pro, so you and I are going through the same frantic learning curve together.... This thread may help....
https://www.gatewaytoairguns.org/GTA/index.php?topic=152800.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=152800.0)
I've been getting lots of advice there from Matthias in particular.... Igor seems eager to make changes to help us, which is nice.... He recently added the GS and GL drag functions....
Bob
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Douglas, it is simply that nobody has bothered making BC measurements at different velocities, not that the BC doesn't change.... Also, there are no NOE bullets listed, which is very disappointing.... I have an idea, however.... What about this?....
If we use the calculated BC from the NOE drawing as a baseline....
(http://noebulletmolds.com/NV/images/N.O.E._Bullet_Moulds_225-39-FN_GC_B2__Sketch.Jpg)
and input the dimensions into the Kolbe Bullet Drag Calculator....
http://www.geoffrey-kolbe.com/drag.htm (http://www.geoffrey-kolbe.com/drag.htm)
It spits out the BC at different Mach numbers.... I did that for the NOE version of the 225107 (above).... SD is 0.107....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/NOE%20225107%20Drag_zpsukzgcvfh.png) (http://s378.photobucket.com/user/rsterne/media/Ballistics/NOE%20225107%20Drag_zpsukzgcvfh.png.html)
This may allow us to get a rough idea of the subsonic BC, which I am 90% certain is NOT what the NOE program is calculating.... It also shows a plot of Cd vs Velocity, to give you an idea of where the sudden drag increase occurs in the transonic....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/NOE%20225107_zpsar95w22a.png) (http://s378.photobucket.com/user/rsterne/media/Ballistics/NOE%20225107_zpsar95w22a.png.html)
In the case of the 225107, that is at about Mach 0.9 (~ 1000 fps)…. I know it's still only calculations, but better than nothing, perhaps.... Don't forget that Cd plot is NOT what the BC is doing, to get the BC you have to compare that to the Cd curve for the G1 projectile (orange line below)....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/Drag%20Coefficients_zpsmvh8fg13.jpg) (http://s378.photobucket.com/user/rsterne/media/Ballistics/Drag%20Coefficients_zpsmvh8fg13.jpg.html)
At least is might give you some indication of what the subsonic BC might actually be, compared to the NOE listed one.... Remember, the BC = SD / FF.... We can estimate the FF by using the Cd (bullet) / CD (G1)…. At Mach 1, just lifting the Cd's from the graphs above, at Mach 1 we would get....
FF = 0.42 / 0.48 = 0.875…. Then BC = SD / FF = 0.107 / 0.875 = 0.122.... Note how that matches up with the BC from the Kolbe calculator (which is rounded to 2 decimals)…. and is not too far off the NOE (calculated) value of 0.128.... If you want it at 900 fps (Mach 0.8 ), we should be able to do that as well....
FF = 0.21 / 0.25 = 0.84.... Then BC = 0.107 / 0.84 = 0.127.... almost exactly what NOE says....
And at Mach 0.5, we would get....
FF = 0.20 / 0.20 = 1.00.... Then BC = 0.107 / 1.00 = 0.107.... That agrees with the Kolbe calculations for Mach 0.5....
HEY HEY !!!!…. I think this could work.... 8)
Bob
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Here is a more detailed plot of the G1 drag function over the velocities we are interested in....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/G1%20Drag%20Profile_zps7o5uthoz.png) (http://s378.photobucket.com/user/rsterne/media/Ballistics/G1%20Drag%20Profile_zps7o5uthoz.png.html)
You may want to save that and print it out for your convenience.... If you click on it, you will see a larger version.... Exact same plot, but vs Mach Number, which may be better to compare with the Kolbe Cd output graph....
(http://i378.photobucket.com/albums/oo221/rsterne/Ballistics/G1%20Drag%20vs%20Mach_zps4xauawqq.png) (http://s378.photobucket.com/user/rsterne/media/Ballistics/G1%20Drag%20vs%20Mach_zps4xauawqq.png.html)
Bob
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I ran across this tonight, and it appears to be a fabulous resource.... http://www.accurateshooter.com/ballistics/bullet-database-with-2900-projectiles/ (http://www.accurateshooter.com/ballistics/bullet-database-with-2900-projectiles/)
It has over 3900 bullets, including many cast bullets.... You can access the data by caliber, and sort by manufacturer, weight, length, or other factors.... It gives the Sectional Density (SD), and the Ballistics Coefficient (I assume G1) at different velocities (if known).... As an example, here are the results for the popular Lyman 257420....
SD = 0.148
BC above 2200 fps = 0.129
BC above 1800 fps = 0.152
BC above 1300 fps = 0.18
BC above 800 fps = 0.20
BC below 800 fps = 0.15
I have only just begun to explore this database, but wanted to share it with all of you....
Bob
Bob
In my Quick Load Ballistic's program, which has 3 sections,
Main QL= which figures powder/bullet computations, and then this info is available into Quick Target set up section etc,
and has 150+ pellets listed etc.
Quick Target Unlimited program = which features any set up from any QL predictions, + you can set any CD/BC,
Drag models = 15 different choices from SAAMI standard to Ingall's and or load from your file you created,
for any projectile you have etc.
These Drag Models are,
G1 = SAAMI standard model,
G2 = Aberdeen J project - conical head,
G5 = Short 7.5* boattail-9.16 cal. tangent ogive,
G6 = Flatbase 6 cal. secant ogive,
G7 = Long 7.5* boattail - 10 cal. tangent ogive,
G8 = Flat base. 10 cal. tangent ogive,
GL = Blunt lead nose,
GS = Spherical 9/16 SAAMI,
GS = Spherical = Don Miller,
RA4 =.22 Rimfire,
Soviet 1943,
Brit= British 1909 British Hatchers Notebook,
Ingalls,
Load from a file,
Would any of these Drag Models be useful for what you are doing?
QT main = shows the projectiles flight to the target, you can also set the velocities for any projectile,
and on the main screen you can check any point/distance etc.
When I entered the same info you have for the Lyman cast bullet 257240,
QT Unlimited shows the same info you have posted for this bullet etc.
I have never played with these sections/programs very much,
except to enter the main bullet I am using/testing, and see what the expected results might be,
to get me close for a long range target etc.
The results I got were close enough for what I was doing and then I could adjust from there.
I am playing around it with the pellets etc. ;)
Tia,
Don
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HI Don....
It depends on how they are stored in your program.... If they are just a column of numbers for the Mach # / Velocity and the Cd, I already have those.... If they are equations that calculate the drag models, then they could be most useful.... I have the G1 that way, but would like equations for the G7, GS and RA4, and of course the GA, which nobody seems to have....
Bob