Since I'm bored, and trying to calm down after breaking the tray of my CDRW (cutting myself in the process), damaging my computer tower and cutting my hands up trying to take the drive out and fix the tray, I'll calculate some physics from this.
First I have to convert these archaic American units. I can't work in such weird, hard to use non-decimal systems.
The rifle weighs = 13.6 Lb (6.2 kg in real units).
The bullet weighs = 720 grain (0.047 kg).
Muzzle velocity = 2600 fps (792.5 metres/second).
First I want to calculate the momentum of the bullet as it left the muzzle, so I can calculate the momentum of the gun jumping backwards. Momentum is the product of mass and velocity, so:
M = m*v
This number would meaningless in itself, but we can insert it into a balanced equation where the momentum of the bullet is m2*v2 and the momentum of the gun moving back in recoil is m1*v1. Since they are equal (every action has an equal and opposite reaction), we can equate them. We also know three of the values so we can plug them in to get the fourth.
m1*v1 = m2*v2 => 6.2*v1 = 0.047*792.5
Rearranging algebraically gives:
v1 = (0.47*792.5)/6.2 = 60.1 m/s
Which means the rifle jumps back at 60.1 metres per second (134.4 mph, or 197.2 feet per second). Imagine 14 Lb hitting your arm at 134.4 mph.
If this isn't impressive enough, we can calculate the force applied by this. Since almost all of it is applied over a very short time, and I can't be arsed, I won't calculate impulse. First, to get acceleration we'll *assume* that the speed of 60.1 m/s is reached only in a fiftieth of a second, 0.02 s. Acceleration is the quotient of velocity and time, so
A = v/t = 60.1/0.02 = 3005 m/s².
And force is the product of mass and acceleration:
F = m*a = 6.2*3005 = 21700 newtons.
21700 newtons is roughly equivalent to a weight of 2170 kg, or 2.4 tons, or 16125 foot-pounds (as opposed to the 11000 foot-pounds force advertised). Although 2.4 tons sounds a lot, it's only applied for a very short time.
So basically it was incredibly DUMB to fire that kind of rifle without a recoil damper or a tripod, and if it hasn't spun out of his hands it would probably totally shattered his collarbone. Now you know the physics reasons why.
Nobody that stupid should be allowed a lighter, never mind a gun.
Just feel pity for anything on the other end of the bullet. If the bullet was brass it could pentrate about 15mm of plate steel, if it was steel about 30mm, if tungsten about 45mm, if DU about 60mm (enough to knock out a WW2 tank with a decent hit). A human being would be transformed into a pile of shapeless flesh by the passage of the supersonic shock wave alone. Obviously one not suitable for 'protecting your property' with, unless you are being attacked by armoured vehicles and have a very, very strong arm. Or are just incredibly thick and think big guns are cool.
