Why are my BC(s), nowhere near the manufacturers or online databases? I chronograph at the muzzle, 10 yards and 20 yards, then I use Chairgun Pro to calculate using velocity change. When I use the manufacturers or online BC, the speeds are nowhere near my chronograph readings. .22, H&N Baracuda Green, 12.50gr = .0854, 12.65gr = .0497. Most of the hunting I do is within 35 yards.
Ballistic Coefficients
- Thread starter gamyrick
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Make sure wind is no factor and several shots are averaged into your data 1st then that being true there is nothing but chronograph error or calculation error left to be wrong I'm thinking. Real world data is not disputable if all factors(temp,moisture,altitude/air density) are properly factored into the equation. Your real data for your specific situation is what to go by. I find this interesting. Bill
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I believe velocity has a critical effect on BC. The faster the pellet travels, the lower the BC. If you are shooting your pellets at a different velocity than the velocity tested in the database, you will get a different BC. It is a bit like throwing a wadded up paper ball. The harder you throw it, the more air-resistance pushes against it. A light toss often decreases the air resistance and you get a better throw. This is a big reason why pellets generally don't do well above 925 fps or so.
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Your first reading (nearest) should be somewhere around 1 yard away from the muzzle. The BC can be affected by where you take the readings between. Too much to type and explain at the moment, but that's what is causing it. Take the readings at 1 yard, and at 50 yards and you should be close to the readings you're seeing on the threads here (I've posted several threads on BC measurements already).
Sean
Sean
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Thanks for your help.
Bill: I test indoors (no wind) using the averages from a 14 shot string.
M. Mahoney: 12.65gr (856fps at muzzle, 832fps at 10yds) 12.50gr (827fps at muzzle, 814fps at 10yds) I don't have the form with me, so I don't know the 20yds numbers.
Sean: My first reading is within 12 inches of the muzzle. I have a TX200, so most of my hunting is done within 35yds. The furthest shot that I've taken since 2012 is 42yds.
I'll Chronograph my pellets today using 1yard and 40yards. I'll try plugging in the numbers separately and then averaging the BC(s) together. I'll post the results tomorrow.
Thanks
Bill: I test indoors (no wind) using the averages from a 14 shot string.
M. Mahoney: 12.65gr (856fps at muzzle, 832fps at 10yds) 12.50gr (827fps at muzzle, 814fps at 10yds) I don't have the form with me, so I don't know the 20yds numbers.
Sean: My first reading is within 12 inches of the muzzle. I have a TX200, so most of my hunting is done within 35yds. The furthest shot that I've taken since 2012 is 42yds.
I'll Chronograph my pellets today using 1yard and 40yards. I'll try plugging in the numbers separately and then averaging the BC(s) together. I'll post the results tomorrow.
Thanks
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All testing was done indoors using the red alpha chronograph. I shot one 12 shot string with each pellet at 1yrd, 10yrds, 35yrds and 50yrds, all fps readings are the average of the shot string. All BC(s) were calculated with Chairgun Pro, using the velocity change option.
H&N Baracuda Green 12.65gr: 1yrd - 856fps, 10yrds - 830fps (BC=.0407), 35yrds - 780fps (BC=.0506), 50yrds - 690fps (BC=.0294)
H&N Baracuda Green 12.50gr: 1yrd - 827fps, 10yrds - 814fps (BC=.0854), 35yrds - 783fps (BC=.0840), 50yrds - 655fps (BC=.0263)
Sean is absolutely correct, the drop off is considnrable at 50 yards and the BC changes drastically. I used 35yards because most of the hunting I do is within that distance. From now on I'll use 1yrd, 10yrds, 35yrds and take the average. The 50yrd BC(s) are in-line with those of the manufacturer.
Thanks again
H&N Baracuda Green 12.65gr: 1yrd - 856fps, 10yrds - 830fps (BC=.0407), 35yrds - 780fps (BC=.0506), 50yrds - 690fps (BC=.0294)
H&N Baracuda Green 12.50gr: 1yrd - 827fps, 10yrds - 814fps (BC=.0854), 35yrds - 783fps (BC=.0840), 50yrds - 655fps (BC=.0263)
Sean is absolutely correct, the drop off is considnrable at 50 yards and the BC changes drastically. I used 35yards because most of the hunting I do is within that distance. From now on I'll use 1yrd, 10yrds, 35yrds and take the average. The 50yrd BC(s) are in-line with those of the manufacturer.
Thanks again
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Glad that started to get you results that were more what you expected. If you wnat to learn a bit more about BC’s and airguns, I suggest you start searching and reading a bunch of the info that Yrrah (Harry) has posted here and on other forums-he’s a wealth of knowledge and experience. I have posted some test data from .25 and .30 cal (what I shoot) if you are curious to see results from those tests.
I agree with the others though: if you are only shooting out to 35 yards, either test for BC there or just sight it in and shoot it. Chairgun has a good sighting calculator to help determine where to sight your gun if you kust want to hold staright on target within a certain size kill zone (your choice of size).
BC’s are really more useful when shooting longer distances (like 75 - 200 yards)...
Sean
I agree with the others though: if you are only shooting out to 35 yards, either test for BC there or just sight it in and shoot it. Chairgun has a good sighting calculator to help determine where to sight your gun if you kust want to hold staright on target within a certain size kill zone (your choice of size).
BC’s are really more useful when shooting longer distances (like 75 - 200 yards)...
Sean
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Again you're correct. My aim points out to 35 yards didn't change, whether the BC was .0497 or .0186. Although the energy changed considerably.
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