Monday, March 30, 2015

How Far Do They Fly?

Sunday afternoon we were shooting CDFA wax bullets in the back yard, and I determined to estimate a maximum range for that load.  It shoots a little 17 grain, .45 caliber wax bullet, propelled by a #209 shotgun primer.  It's fairly low powered as handgun ammo goes, but we wonder about such things, especially if we're shooting in a suburban neighborhood.  The neighbor downrange is easily 200 yards away.

So, the boys and I walked out to the pond to shoot across the glassy surface of the water, to see if we could identify a splash, and try to estimate the maximum range, in case a bullet gets past my backstop.

I don't have chronograph data, but the CFDA estimates that a common 209 load will travel about 650 fps.  When we got ready to take the shot, I was standing about five (5) feet above the water, holding the revolver five (5) feet above ground level, and holding it more or less level.  I had three good pair of eyes watching for the bullet splash and was aiming at a small island about 100 yards from my shooting position.

At the shot, we strained our eyes, looking for the splash, and my son said "Hell, Dad, there it is right there."

I was peering across the water.  "Where?"

"About 40 yards."  He pointed less than halfway to the island. "You can see the wax bullet floating in the water."

I looked down, and sure enough, that little orange bullet was floating less than 40 yards away.

So now we know.  The standard CFDA #209 load will travel about 40 yards more or less.  Certainly further study is in order, but I don't have to worry about neighbors finding wax bullets in their yard and wondering what the hell I'm doing.


Daddy Hawk said...

Gravity causes objects go fall at 32 feet per second more or less. That means it took your wax bullet .15625 seconds to fall 5 feet. In that time, it flew 33.85 yards.

Anonymous said...

Five feet? I thought you said five plus five - the ground was five feet above the water, and the gun was five feet above the ground.

My college physics is rusty, but I seem to recall that it takes one second to fall the first sixteen feet.

call it around 2/3 second to fall ten feet, and you get an average velocity of ... um, 200 fps? Muzzle velocity would be higher, slowing down all the way.

Another thing - how far would it go if you elevated the muzzle? Your neighbors might want to know.

Old NFO said...

Good to know. :-)

Daddy Hawk said...

Anonymous, my college physics is rusty too which is why I was trying to take the SWAG approach.

To be accurate, gravity accelerates objects at approximately 32 feet per second squared. So, in the first second, the falling object goes from a dead stop to a speed of 32 feet per second, 64 feet per second in the second second, etc. until terminal velocity is reached.

I may have misread PawPaw's description and failed to account for the additional 5 feet. PawPaw gave his own caveat that the barrel was more or less level. A 1 or 3 degree elevation difference from level won't change the range appreciably. A 45 degree barrel elevation would get the greatest range.

So, let's be generous and call it 10 feet with a perfectly level barrel. Also, to be fair, I was horrible at Calculus and never learned to cheat at it like most people figure out. So, I'm going for simple math that will get us in the right ballpark.

We know the bullet fell less than 32 feet. So, it was falling at some speed greater than 0 FPS and less than 32 FPS. Assuming constant acceleration, it would take no more than .3125 seconds to fall 10 feet. Once again applying the estimated muzzle velocity, that yields an estimated range of 67.71 yards.

PawPaw estimated the distance to the spent bullet at 40 yards. So, either the original calculation is closer to accurate, PawPaw's point of aim was unconsciously a few degrees below level, the ammunition was traveling less than 650 FPS or there was a really big gust of wind in his face when he shot.

Of course, I could be wrong.