# Internal Ballistics

1. Jun 16, 2009

### Ardem

Hi guys,

I am hoping some one can help me out here and after some forumlas and very basic ones at that on internal ballistics. There is a heap of information out there and they tend to jump straight to the hard stuff which tends to be tough on a novice like myself.

I have done a heap of googling and the formulas are either totally over my head or not what I am after.

The formulas are based around ww2 tank guns, so caibres of 20mm up to 120mm

I have some real world figures below, but cannot work out the relationship that can determine the muzzle velocity from the powder mass

diameter=37mm shellweight=.600kg cartridgesize=145mm velocity=670m/s barrellength=37.7 calibre

diameter=50mm shellweight=2.06kg cartridgesize=419mm velocity=835m/s barrellength=60 calibre

diameter=75mm shellweight=6.8kg cartridgesize=495mm velocity=740m/s barrellength=43 calibre

The formula I have come up with just does not cut it. I was using X as a pseudo factor to get the rough estimates so Force would equal Force. As you can see I am far from a physics genius and that why I need help.

P = Volume of Powder
X = Explosive force Factor
m = shell mass
v = velocity

PX = mv^2

sqr (PX / m) = v

Now I know there huge amount of factors that add and subtract but I am after even ballpark forumla based on powder being the same quality and power, shells the same aerodynamic velocity.

What I am trying to achieve is if I know the powder volume and the shell weight and the calibre, what is the muzzle velocity

Please remember to keep it simple and a example is always great, thanks for any help that can be given.

2. Jun 16, 2009