My game system is split into two parts, a Core system which all genres, settings and premises must have, and a Plug-in system which provides mechanics, attributes, the chargen process and other elements which are more genre or settings-bound.

I wanted to create an Engineering Manual which would be a Plug-in resource for players or the GM to create weapons, vehicles, and system equipment (such as communications or sensory gear). Because my game is quite crunchy and more grounded into the sense that "this could really happen" and "these are the things I'd have to worry about if I did this in real-life".

Right now I'm trying to develop rules for weapons. Being a neophyte computer programmer, I've been abstracting the concepts as much as possible in order to seperate the essence of something from its actual behavior. I'm doing this so that I can take what's common about weapons and create the same traits to describe them.

For example, I've broken weapons down like this:
The Damage Object(DO)- The DO is what actually delivers the form of damage to the target. It is the means by which the DO's energy is transferred to the target to change the target's current state. In the case of a gun, it's a bullet, in the case of the sword, it's the sword itself. In the case of the former, it's an Indirect DO, and in the latter it's a Direct DO.

The Delivery System- How does the DO get to the target? There can be an Internal Delivery System (such as a rocket), an External Delivery System (like a gun or bow and arrow), or Self-Propelled (most forms of energy weapons like lasers where the DO is also the means of propulsion)

Damage Form- What form of damage does the DO do? Generally, it is either kinetic (a moving object colliding with another object), energy (a form of energy releasing its energy to the target), or Pathogen (a catch-all that describes any vector which can state change one of the Damage System Tracks of a character....for example, diseases, poisons, mental trauma, etc)

Damage Type- How does the DO affect the state change on the target? In Kinetic DO's, it is physical damage and can be either penetrating, tearing, crushing, cavitating or cutting. Energy forms can either do Heat or Radiation damage. Pathogens directly affect either an attribute, or one of the Damage System Tracks (of which I have several).

Right now, I'm concentrating on developing normal conventional weapons with the above abstractions in mind, and I need to make the above elements more concrete. I've been very much influenced by Greg Porter's excellent Guns! Guns! Guns!, but I think there can be some room for improvement. For example, 3G! combines the element of kinetic energy and pressure into one value...the Damage Value. I think that's problematic. I want my game to seperate a round's ability to penetrate armor seperately from how much tissue damage it does.

This leads to the next problem. From doing a little research on Terminal Ballistics, the general consensus now is that total Kinetic Energy of a round doesn't really have that much of an impact on how damaging a bullet is. The greatest determiner of Wounding Capacity (WC) is how big of a hole it creates in you. For example, some very high powered rifles with solid metal jackets drill nice clean holes in their targets, whereas a slower bullet when it hits the body often tumbles, leaving a very jagged wound track inside the body. Moreover, the bullet may not exit the body, and hence, 100% of the kinetic energy of the round is absorbed by the body.

So this leads me to Question #1: How to determine a Damage Rating (Terminal Ballistics). From my research, it seems there are a couple factors which help determine how big of a wound cavity you leave in the target.

Round Tumble- The more yaw or pitch a bullet has, when it hits the target, this becomes more pronounced, causing the flight path of the bullet to go in less of a straight line, and more into a jagged pattern

Round Fragmentation- Some rounds will actually break apart upon hitting a body, so that multiple wound channels are created

Round Deformation- Hollow Points take advantage of this. When the bullet hits a target, it mushrooms creating a much larger wound channel

Round supercavitation- The russians came up with a round that when fired, creates a wall of supercompressed air around the bullet (the nose of the bullet has a slight concave curve to it to create this pocket). When the bullet hits the target, this pocket of air collapses doing two things. First, it creates a shcokwave in the human body. Research says that this probably only has minimal impact on tissue damage. But the other effect is that when the air pocket collapses, it makes the bullet pitch or yaw, making the bullet tumble inside the body. NATO forces don't use this round (even though it's not specifically forbidden by the Geneva convention) as they feel it is inhumane.

Does anyone know of any good ways of how to model this or of any good sites that can explain how this works better?

Question #2: Develop the ammunition first or the gun first?

In 3G!, you sort of co-develop them at the same time. Or rather, you decide on a Damage Value, and from that you determine what the muzzle energy of the gun is, and the base energy of the ammunition. However, in my design system, Damage isn't directly correlated to the energy of the gun. So I was thinking that I'd probably have to design the gun first.

I was thinking it'd go something like this:
1. Figure out what kind of aiming ballistics you want (how accurate it is...generally dependent on velocity and length of barrel)
2. Determine what kind of damage ballistics you want (how quickly does the round lose its kinetic energy?). Rifle rounds keep their energy longer than pistol rounds.
3. From the generalizations above, figure out an approximate velocity of the gun you want as well as the bullet's inherent characteristics like mass, length/diameter ratio...or caliber (these should be independent of what theExternal Delivery System provides).
4. Determine how much energy the Delivery System needs to propel the givenmass of the bullet to the desired velocity.
5. From this, determine the mass of the different components of the External Delivery System (the Receiver, Action, Feed Mechanism, Barrel and Ergonomics)

My system will probably at least seem very familiar to anyone who's used Guns! Guns! Guns!, but there will be some slight differences. Namely how Damage and Penetration are calculated, and mine will have a few extra steps (like considering the cross sectional area of a round to determine Drag and Penetration). But these few small changes means that I can't follow in the footsteps of 3G! either, because some of the steps rely on knowing the Damage Value which I don't use.