Firing into overhead trees Air Rifle Vs Rimfire both .22

ivanthehunter

Ye Ye i know don't fire a bullet when you cant see the back stop. But i would just like to know the difference between the two in terms of safety.. I understand the dynamics of sat a .22 fired in to the trees but what about the little brother an air rifle say .22 or even a .177. The air rifle has lets say 700ft sec but I'd imagine that it weighs a lot less and travels a lot less.. that skirt on the pellets must cause considerable drag..
what do the pro's think.

Mellor

I think it was mentioned on the other thread that an air-rifle would be acceptable. Or a shotgun, the range and weight of each mean that it is unlike to hit anyone

Rovi

Using Sierra's [FONT=Verdana, Arial, Helvetica, sans-serif]Infinity Ballistics software with relevant data gives the following results-[/FONT]

(Note- I used the data here: http://extorian.co.uk/shooting/pellets.html and here: http://www.compasseco.com/blog/2007/02/ballistic-coefficient.html to get weight and Ballistic Coefficient data for airgun pellets, so they're very much 'ballpark' figures, but should be close enough for this)

.177 airgun pellet (10grain, 0.020BC) @ 800fps:
The maximum range of your Custom .177 .17 airgun pellet 10gr at 800 Feet per Second is: 374.5 yards at an elevation angle of 30 degrees.

.22 airgun pellet (20grain, 0.020BC) @ 800fps:
The maximum range of your Custom .22 airgun pellet 20gr at 800 Feet per Second is: 374.5 yards at an elevation angle of 26 degrees.

.22LR hollowpoint bullet (40grain, 0.110BC) @ 1300fps
The maximum range of your Custom .22LR hollowpoint bullet 40gr at 1300 Feet per Second is: 1602.4 yards at an elevation angle of 27 degrees.


I'm very much open to correction on the above, but I think it's a decent enough illustration of the differences between the various projectiles.
I'll repost most of this plus some data on centerfire cartridges over on the other thread.

milkerman

Hi Rovi,
Do you know the final velocity and kinetic energy for each projectile at the ranges given above. It's one thing to know the maximum range, but what damage could they inflict?

Mellor

Kinetic energy is mv2, so if its possible to work out the velocity from the drag then its possible. Terminal velocity of a bullet is about 150 ft/s (from other thread too), so thats 45 m/s. A grain is 65 mg so, 40 grain is 2.6g or .0026 Kg
45x45x.0026= 5.3J

Then again, the above is about as accurate as the original figures.
If somebody has more accurate fiigures for velocity than adjust accordly. Some else might also so a calc in ft lbs

IRLConor

According to the page here (using the same data as Rovi):

http://www.eskimo.com/~jbm/calculations/traj/traj.html

the energies work out like this:

                  100yd  200yd  300yd  400yd  500yd  600yd  700yd  800yd
.177 Air Gun      5.1J   1.1J   0.2J     -      -      -      -      -
.22 Air Gun      10.3J   2.3J   0.5J     -      -      -      -      -
.22lr HP        118.0J  86.0J  66.0J  51.3J  39.9J  30.8J  23.6J  17.8J