You are correct, ChairGun can correctly calculate the BC for a given set of numbers (starting and ending velocity, and distance between them)…. However, if you calculate the BC between 900 and 800 fps, don't expect it to be correct between 700 and 600 fps.... or 500 and 400.... The drag models used just don't match our pellets closely enough.... As a pellet slows down going downrange, it's Drag Coefficient changes.... The model used (in ChairGun you should use GA for pellets, and G1 for bullets) does this as well, but not in precisely the same manner.... Since the BC is the ratio of your Cd and the Cd of the drag model used, the BC can (and usually does) change with velocity.... Quote Now lets just say chair gun has got it right with the BC and 553.5 = 0.0225 and 912= 0.0363 we can use chairguns BC calculator velocity box to get the BC for any FPS . This statement is only correct if you already KNOW the near and far velocities and the distance between.... If you calculate a BC of 0.0225 from your 553-416 fps measurements and then change only the MV to 912 fps and click "Calculate", Chairgun will use the BC previously calculated of 0.0225 and give a MUCH lower result than the correct number of 807 fps.... Bob
Now lets just say chair gun has got it right with the BC and 553.5 = 0.0225 and 912= 0.0363 we can use chairguns BC calculator velocity box to get the BC for any FPS .
The BC varies depending on velocity because the drag models used don't work well for pellets.... Using the G1 drag model (the most common), for the JSB Exact Jumbo 15.9 gr. it is about 0.032 at 700 fps, increases to 0.042 at 800-850 fps, and then starts dropping again, to about 0.032 at 950 fps, and then it really starts to tank above that.... The best way to find out your drop for your pellets in your gun is to shoot at various ranges and record them....Bob
What part of "out of date" don't you get?.... That chart is over a decade old, and based on insufficient data....I have tried my best to explain this to you and failed.... So I'll just leave you to try and figure it out on your own.... Good Luck....Bob
I was talking about the jsb 15.89 pellet not every pellet made . If you watch the video I post above . Take the numbers you see in the video for the 15.89 pellet that he list at the different distances for the 553.5 fps and ending at 416.4 at 50 meters they all are the same in the chairgun program . So his real life shooting of the pellet through the crony at the different distances match what chair gun comes up with . So no matter what gun chairguns formula match the real life numbers at the different distanced he listed . As I said in the above post once I entered the pellet weight, end distance of 50 meters and muzzle velocity at 553.5 I scrolled down on the table so I could see the fps at 50 meters I changed the BC numbers until the fps matched 416.4 the crony's fps at 50 meters . Once the 50 meter 416.4 was meet by changing the BC all the other fps 's matched the real life numbers . Chair gun didn't know the barrel twist or what damage the pellet went through the barrel but it came up with the same numbers as the real life numbers . I think there is something to this . If you can match real life numbers like the muzzle vel and the end distance velocity you can just enter that into chair gun and get its BC . Now if you change the fps of the muzzle vel to 912 fps and match that to the 807 fps at 30 yards like in the link of BC that someone post chair gun comes up with the BC of 0.0363 . This BC matches the 807 fps at 30 yards . The 0.0310 BC . in chairgun at 30 yard distance showed 791.9 not 807 fps . What I'm getting at is chairgun matched every distance the same as real life flight from 553.5 to 416.4 So if chair gun got it right then I would think chairgun would get it right from 912 fps to 807 fps at 30 yards . So for real life results I would go by the chairguns BC that made the 807 fps to match with its BC number of 0.0363 because chair gun nailed the real life numbers at the 553.5 fps to 416.4 fps numbers . Now lets just say chair gun has got it right with the BC and 553.5 = 0.0225 and 912= 0.0363 we can use chairguns BC calculator velocity box to get the BC for any FPS . In chair gun once you entered the BC number you think is correct if you right click your pointer over the BC number it will open up a box where you can choose calclulate BC from : and then choose velocity change . I entered the 0.0363 bc number and once the window is open you can change velocity from 912 to 553.5 and the range to 50 meters and the 807 to 416.4 and then press calculate and sure enough it gave me the same BC I had that worked out in the video of 553.5 = 0.0225 . So I think the right BC for this pellet is 0.0363 at 912 fps . With this box in chairgun once you have the correct BC at one muzzle vel you can have it for any muzzle vel with the same pellet and you can figure out the BC for every fps gun there is if you know the muzzle vel and end distance vel . Try it out in chair gun and see for your self 0.0363 set at 912 v1 30 yards and 807.0 v2 . and you will see that BC puts the pellet at 807 fps at 30 yards and it matched the videos results from the 553.5 fps gun .
Quote from: rsterne on July 11, 2018, 12:17:40 PMWhat part of "out of date" don't you get?.... That chart is over a decade old, and based on insufficient data....I have tried my best to explain this to you and failed.... So I'll just leave you to try and figure it out on your own.... Good Luck....BobFine Bob don't have to be douche bag about it. Take the chart off the forum marking it as bad data so no one else makes the mistake of re-posting so called Bad data. So his answer to simple question is to go FULL BABY and give no answer at all. Thanks for nothing Bob.Simple question BC of JSB 15.89 (Very common round) even gave the speed of 870 fps.Only requires simple answer like "Here ya got .xxx" done. Ranting on and on does no one any good.
Quote from: rws45user on July 09, 2018, 07:37:20 AMI was talking about the jsb 15.89 pellet not every pellet made . If you watch the video I post above . Take the numbers you see in the video for the 15.89 pellet that he list at the different distances for the 553.5 fps and ending at 416.4 at 50 meters they all are the same in the chairgun program . So his real life shooting of the pellet through the crony at the different distances match what chair gun comes up with . So no matter what gun chairguns formula match the real life numbers at the different distanced he listed . As I said in the above post once I entered the pellet weight, end distance of 50 meters and muzzle velocity at 553.5 I scrolled down on the table so I could see the fps at 50 meters I changed the BC numbers until the fps matched 416.4 the crony's fps at 50 meters . Once the 50 meter 416.4 was meet by changing the BC all the other fps 's matched the real life numbers . Chair gun didn't know the barrel twist or what damage the pellet went through the barrel but it came up with the same numbers as the real life numbers . I think there is something to this . If you can match real life numbers like the muzzle vel and the end distance velocity you can just enter that into chair gun and get its BC . Now if you change the fps of the muzzle vel to 912 fps and match that to the 807 fps at 30 yards like in the link of BC that someone post chair gun comes up with the BC of 0.0363 . This BC matches the 807 fps at 30 yards . The 0.0310 BC . in chairgun at 30 yard distance showed 791.9 not 807 fps . What I'm getting at is chairgun matched every distance the same as real life flight from 553.5 to 416.4 So if chair gun got it right then I would think chairgun would get it right from 912 fps to 807 fps at 30 yards . So for real life results I would go by the chairguns BC that made the 807 fps to match with its BC number of 0.0363 because chair gun nailed the real life numbers at the 553.5 fps to 416.4 fps numbers . Now lets just say chair gun has got it right with the BC and 553.5 = 0.0225 and 912= 0.0363 we can use chairguns BC calculator velocity box to get the BC for any FPS . In chair gun once you entered the BC number you think is correct if you right click your pointer over the BC number it will open up a box where you can choose calclulate BC from : and then choose velocity change . I entered the 0.0363 bc number and once the window is open you can change velocity from 912 to 553.5 and the range to 50 meters and the 807 to 416.4 and then press calculate and sure enough it gave me the same BC I had that worked out in the video of 553.5 = 0.0225 . So I think the right BC for this pellet is 0.0363 at 912 fps . With this box in chairgun once you have the correct BC at one muzzle vel you can have it for any muzzle vel with the same pellet and you can figure out the BC for every fps gun there is if you know the muzzle vel and end distance vel . Try it out in chair gun and see for your self 0.0363 set at 912 v1 30 yards and 807.0 v2 . and you will see that BC puts the pellet at 807 fps at 30 yards and it matched the videos results from the 553.5 fps gun ....this stuff melts my brain but I read on to try to learn... and...You sir(?) have the singular best avatar ever. ...reminds me of the Mrs at 26... Sometimes even the blind dog finds a bone
Apparently answering the question as completely and politely as I can, many times, doesn't either.... rws45user has his own ideas, that conflicts with reality, so who am I to continue to try and change that.... "FULL BABY" and "no answer at all"?.... You obviously didn't read my FIRST reply, where I answered the OP's question as completely as possible.... back in 2015 when the thread started.... as to being a "douche bag".... …. I guess you never got tired of trying to help someone who just wanted to argue?.... I have no responsibility to keep trying to do that, thank you.... I gave him many answers, he just didn't want to hear them....Bob, I do apologize for not being clear who I was answering, you may have thought my last answer was directed at you, I assure you it was not.... The BC at 870 is probably in between 0.032 and 0.040, depending on what gun.... Bob
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