 |  | | | |  | |  |  | Pellet energy dropoff |  | |  |  | |
 Posted: Mon Apr 19, 2010 6:19 pm |
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| 327Nomad |
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| Who remembers physics class? I am having a good deal of luck eliminating disease-carrying, property-damaging squirrels here in my residential neighborhood. All of my shots have terrific backstops, but on occasion I find a squirrel up a tree denuding branches of sprouts and leaves. If I were to take a shot at moderately upward angle (say 45 degrees), is there a point at which the energy of an 8.3 grain .177 RWS Superdome exiting my Gamo, at <1200 fps, has lost its destructive energy and falls to earth harmlessly a couple hundred yards away, with the energy of a hail stone? With that little mass, I would think the energy bleed off would be rapid, and the trajectory would be anything but parabolic. Don't worry, I haven't tried it yet. Anyone got any ideas? My trees want to know. |
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| Posted: Mon Apr 19, 2010 6:41 pm |
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| rsterne |
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According to ChairGun3.... an 8.3 gr. RWS Superdome starting at 1000 fps (no way you are going to drive that at 1200) will have the following terminal energies:
100 yards : 408 fps (3.1 FPE)
200 yards : 166 fps (0.51 FPE)
Maximum range = 347 yards when fired at 18 degrees : 0.20 FPE
Bob |
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Mon Apr 19, 2010 6:48 pm |
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| fritz |
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If you fire at a high angle, the pellet will actually accelerate on its way down from the top of the parabola.
So you would need to figure how far the pellet would go up, before it comes back down. Then when it starts coming down, gravity accelerates it.
Either way... don't shoot where you don't have a safe back stop...  |
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"I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa
Speed is impressive, accuracy is deadly.
It's not that I'm not a people person, it's just that I'm not a stupid people person. |
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| Posted: Mon Apr 19, 2010 9:25 pm |
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| Lipoly |
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Last edited by Lipoly on Mon Apr 19, 2010 9:35 pm; edited 1 time in total
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Philip
RWS 350 .22 w/Leapers 4-16x50
Crossman 1377 |
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| Posted: Mon Apr 19, 2010 9:26 pm |
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| Lipoly |
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| fritz wrote: |
| If you fire at a high angle, the pellet will actually accelerate on its way down from the top of the parabola. |
Valid point. For reference, terminal velocity of a human is ~180fps. I would be surprised if it were lower for a pellet given the density and relative drag. Keep in mind (according to MythBusters) if you shoot at too high an angle the projectile will loose its ballistic trajectory and tumble on the way down and thus go way slower than otherwise. |
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Philip
RWS 350 .22 w/Leapers 4-16x50
Crossman 1377 |
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| Posted: Mon Apr 19, 2010 10:01 pm |
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| rsterne |
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| Quote: |
| the pellet will actually accelerate on its way down from the top of the parabola |
Correct.... and the maximum velocity it could reach would be it's "terminal velocity".... My calculations put that at ~120 fps for a .177 cal sphere (which has a better BC than an RWS Superdome).... an 8.3 gr. pellet travelling at 120 fps would have about 0.27 FPE....
My guess is that ChairGun takes the terminal velocity into account in it's maximum range tool....
Bob |
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Tue Apr 20, 2010 8:28 am |
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| Slavia |
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| Quote: |
| My calculations put that at ~120 fps for a .177 cal sphere |
That sounds right. Here's a source where they put the terminal velocity of a .30 Cal. 150 grain Spitzer bullet at 300 FPS, and the B.C. for a pellet would be far worse:
http://www.loadammo.com/Topics/March01.htm |
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| Posted: Tue Apr 20, 2010 10:02 am |
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| Lipoly |
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This is at higher altitude, but still impressive: http://airgunhome.com/agforum/posting.php?mode=reply&t=5172
"Competition speed skydivers fly in the head down position reach even higher speeds. The current world record is 614 mph (988 km/h) by Joseph Kittinger, set at high altitude where the lesser density of the atmosphere decreased drag."
1,260,000grain @ 900fps...thats 2,266,791 FPE! |
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Philip
RWS 350 .22 w/Leapers 4-16x50
Crossman 1377 |
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