vocablery,niether has any real realevence to how powerful or not a gun actually is but are commonally

 used today to doso.

 Both terms are just a calculation based entirely on projectile weight and velocity and dont take into

 account bore size,what projectile is made of or how it will perform on anything but know size and 

 weight steel plate attached to a ballistic pendulum,which was an early form of chronograph that was 

 starting back in muzzleloading days to calculate velocity.

 Joules is the metric equivelent to foot pounds energy,both are simply calculations of how much energy

 it takes to move a known weight object a certain distance,in case of a ballistic pendlum the object

 moved was a known weight steel plate attached to a pendulum.

 A projectile of known weight was fired at pendulum and distance pendulum moved measured,this measurment then used in the reverse of how its used today to then calculate velocity and then used

 to calibrate gun sights or determine the effective distance a gun was usable out to.

 This was a very complicated time consuming process and mainly used by military arsenals.

 today of course we have modern electronic chronographs to do all these things for us,modern chronos

 havnt been around that long,the first electronic chronos came about proberly in 1960s and were very

 different to those today and due to primative electronics didnt have direct digital readouts we take

 for granted today so were not as accurate as evan a cheap chrono is today and time consuming to use

 There is a little history on foot pounds energy and joules an their reavence to a guns performance etc

 Cheers Mike

Good to see a bit of history though, especially as I'm old enough to have used a ballistic pendulum and the first electronic chronographs using light sensors. 

This is a topic that I have been following on the GTA forum. It is extremely complicated accompanied by some fairly intricate mathematics. One facet of pellet trajectory overlaps with another facet to the extent that I have to go back and refresh parts of it.

I got to the stage that it doesn't matter a hoot what the science involves as long as it works and it is a bit of a wonder that it does as well as it does.

Even if you grasp all of the technicalities the shooter still has to point the rifle at the right spot to be use.

Then along comes a puff of wind.

Muzzle energy is just one part of it all.

 its hard to actually define why a projectile specially a small lightweight pellet is so effective,i am 

 continually still amazed just how effective 177 cal pellets really are,my back ground is more in 

 firearms than airguns,was for many years a real lead bullet nutin both handguns n rifles,thats prob why

 i developed a love of airguns,they shoot lead projectiles eh!!

 I posted this topic to get some converstion going on this topic as think there are lot airgun users who 

 have been told lot rubbish bout airgun power etc,and hoping this thread may help some get better 

 understanding on this topic,me i am still trying to figure it out,goin to do some comparision tests using

 a 177 and 22 cal pcp rifles both running at 20 fpe in ballistic gell to see what happens between the two

 Recently seen some tests using 18fpe 177cal using 10.34 jsbs at 50/100yds in gell,still getting large

 wound channels n allmost 300mm penertration at 100yds,bloody amazing,didnt think would be any

 where like that.

 So be interesting to do same tests with both 177/22 at same fpe level and compare.

 Cheers Mike

 their utube channel.

 Cheers Mike

 melt gellitene.

 Cheers Mike