Quote from: rsterne on February 23, 2019, 10:38:31 PMHowever, ES will tell you the vertical stringing on the target, with a larger ES meaning a greater difference between the fastest (highest POI) shot and the slowest (lowest POI) shot.... While it is true that the more shots you fire, the larger the ES will be, when applied to something like an unregulated PCP, where the velocity forms a bell-curve, it is extremely useful to determine the useful pressure range you can use to keep all your shots within the desired velocity spread.... The further the range you are shooting, the smaller the ES needs to be to limit vertical stringing to an acceptable value.... For the most part, the length of the string is limited by the ES you find acceptable.... For that reason I use ES exclusively, I never look at the SD....I'm pretty sure that is what Peter meant when he said "tighten your ES".... ie try and tune the gun, or use the appropriate pressure range, to reduce the ES to an acceptable value for the range you are shooting at.... For the most part a smaller ES is accompanied by a reduction in SD as well.... although an ES of, say 10 fps over 10 shots will have a larger SD than that same 10 fps ES over a 50 shot sample.... That is the point Scott is trying to make, I think....BobOK. We are talking about two different things.You are talking about using ES to determine the number of shots with an unregulated PCP, before pressure falls below the acceptable range. And the last shot will likely be one of the two that determines the ES. ES can be very easy and useful for that. That can be a measure of efficiency and air usage.I am talking about the shot-to-shot consistency of a springer or a regulated gun that has not fallen off the reg. SD tells you more about shot-to-shot consistency. The two ES shots can be any of thousands so in themselves they tell you very little about shot-to-shot consistency.
However, ES will tell you the vertical stringing on the target, with a larger ES meaning a greater difference between the fastest (highest POI) shot and the slowest (lowest POI) shot.... While it is true that the more shots you fire, the larger the ES will be, when applied to something like an unregulated PCP, where the velocity forms a bell-curve, it is extremely useful to determine the useful pressure range you can use to keep all your shots within the desired velocity spread.... The further the range you are shooting, the smaller the ES needs to be to limit vertical stringing to an acceptable value.... For the most part, the length of the string is limited by the ES you find acceptable.... For that reason I use ES exclusively, I never look at the SD....I'm pretty sure that is what Peter meant when he said "tighten your ES".... ie try and tune the gun, or use the appropriate pressure range, to reduce the ES to an acceptable value for the range you are shooting at.... For the most part a smaller ES is accompanied by a reduction in SD as well.... although an ES of, say 10 fps over 10 shots will have a larger SD than that same 10 fps ES over a 50 shot sample.... That is the point Scott is trying to make, I think....Bob
Hack21: I get that, but does the self regulating CO2 effectively crate a flatter bell curve, less ES, until the liquid is depleted and only gas remains? Acting more like a regulated HPA PCP?
Top picture is the old spring kits SD.The bottom picture is the new spring...Which numbers are important? And what do they really mean?
Quote from: DevilsLuck on February 24, 2019, 12:56:15 PMThank you! That is exactly the kind of information I was looking for!Top picture is the old spring kits SD.The bottom picture is the new spring...Which numbers are important? And what do they really mean?"Which numbers are important?"For that calculator, the two most important numbers for me are:"Sample standard deviation, s" and "Mean (Average)"The Sample standard deviation is the the SD in FPS. Mean (Average) is the average velocity in FPS.The average is what you would use for your trajectory calculations (ChairGun, etc).I like to convert the Standard Deviation (SD) to a percentage:Old spring kit:10.05/750.83 x 100% = 1.4%I would consider that unacceptable as 1% is my personal threshold for a somewhat healthy spring gun.New spring kit:4.66/748.95 x 100% = 0.6%That's good, especially considering it's fairly new tune."And what do they really mean?"The SD gives you a confidence level for that velocity.1 x SD will encompass about 68% of the shots2 x SD will encompass about 95% of the shots3 x SD will encompass about 99.7% of the shots4 x SD will encompass about 99.99% of all shotsWhat that means is that out of 100 shots, 68 of them will likely be +/- 4.66fps.And you will almost never see a velocity outside of +/- 18.62fps.
Thank you! That is exactly the kind of information I was looking for!Top picture is the old spring kits SD.The bottom picture is the new spring...Which numbers are important? And what do they really mean?
Hack21: I get that, but does the self regulating CO2 effectively crate a flatter bell curve, less ES, until the liquid is depleted and only gas remains? Acting more like a regulated HPA PCP?Very interesting Bayman...I would think the higher end pellets would be more consistent on ES / SD as the Crosman pellets are harder alloy. Most upper end pellets are soft and the skirt would expand with the air blast and seat more consistently to the rifleing.
SD, then ES....but 2 caveats..... I use AD , average Deviation. No your chrony wont calc it for you, you'll need a calculator and sharp pnecil or a spreadsheet to get it figured. AD will show similar data to SD, just aldightly smaller number. IMO its better than SD, just not as convienent...
Hoosier, the constant velocity of CO2 at a constant temperature is because there is both liquid and gas inside the cartridge, and as you use the gas, the liquid boils off to replace it, and keeps the pressure constant.... If you shoot too rapidly, however, that boiling off, which takes energy, cools the cartridge and reduces the pressure slightly during your shot string.... Once the liquid CO2 is used up, then the pressure drops with every shot, and so does the velocity.... You can tune a CO2 gun to self-regulate over quite a wide range of temperatures with the right hammer strike, but that is a different topic.... Sorry for the side-track....Bob
Quote from: rsterne on February 24, 2019, 12:36:03 PMHoosier, the constant velocity of CO2 at a constant temperature is because there is both liquid and gas inside the cartridge, and as you use the gas, the liquid boils off to replace it, and keeps the pressure constant.... If you shoot too rapidly, however, that boiling off, which takes energy, cools the cartridge and reduces the pressure slightly during your shot string.... Once the liquid CO2 is used up, then the pressure drops with every shot, and so does the velocity.... You can tune a CO2 gun to self-regulate over quite a wide range of temperatures with the right hammer strike, but that is a different topic.... Sorry for the side-track....BobBob with both of my type 1 Crosman 150's I'm getting no less than 80 shots per cartridge on low power and about 30 shots on hi power. It really does add to the enjoyment of indoor shooting on low power with these two pistols. When I test them over the Chronograph on low power I can easily fire 10 consecutive shots with very little variation in fps whereas on hi power it drops considerably every shot until a warmup. Crosman did some great work when they made these guns, hi power is ideal for small pesting and low power is really great for targets. I plan on carrying one this summer when out hunting red squirrel, they're like carrying a holstered 45 IMO and fit the holsters perfect.