Home » MODDING HQ 1.13 » v1.13 Coding Talk » Lower bullet damage with distance
| Re: Lower bullet damage with distance[message #294076]
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Thu, 24 November 2011 13:28  
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 usrbid |
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Messages:1506
Registered:December 2008 |
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Yo Monade, the amount of damage a bullet does depends on (as far as I know):
- bullet weight
- bullet speed (at a specific distance)
- bullet shape
- target medium
From weight and speed you will (probably) be able to calculate the energy the bullet has. However as far as I know the energy is not the best measure to determine damage. There is something called the Taylor KO Index (look on Google), which is better in predicting effect on impact.
The weight, speed, and energy for most bullets you can find on Wiki (or on the package when you purchase them e.g. Hornady is good about that).
For example shooting a typical 9mm and 45 ACP under same conditions, it is quite possible the 9mm will have more energy compared to the 45 (I haven't verified that), however from experience the 45 will have more destructive effects (I believe because the bullet is bigger and heavier).
A hollow point will penetrate less compared to a full metal jacket. For example shooting a 45 HP and FMJ under same conditions the FMJ will travel further in the medium.
Here is why energy alone is not a good measure. A 9mm FMJ will travel ~4 feet through ballistic medium (no denium in front), while a 45 FMJ will make it (I guess) ~18 inches (maybe more, but not 4 feet). The 9mm travels further because the bullet is smaller and there is less friction to slow it down.
However a front to back pass through is not as desirable. Depending what organs (if any) were damaged, this can be survivable. A 45 HP will lose all its energy inside the medium and cause a tremendous temporary stretch cavity and leave a huge wound channel which in turn speeds up blood loss.
Bullet speed at muzzle (right in front of the gun) is determined by the barrel length (using same bullets). Too short of a barrel doesn't allow all energy from the powder to be transferred on the bullet. Too long of a barrel (unlikely case) will eventually slow down the bullet due to friction in the barrel.
For example shooting a 45 ACP through a 5 inch barrel will have the usual 890 ft/s at muzzle, shooting through a 3 inch barrel can make the speed drop below 800 ft/s. US soldiers in Iraq prefer 20 inch barrels for 5.56 NATO as the longer barrel gives the bullet more speed / destructive power.
Bullet speed at target is influenced almost entirely by air resistance, which in turn needs humidity, barometric pressure etc. For example most modern firearms e.g. Glock, H&K USP will discharge safely completely submerged in water, however the bullet travels about 2 1/2 feet in water.
Another example, the faster a bullet goes the more air resistance it will encounter. Speeding up a bullet to somewhere between 3,000 to 4,000 ft/s will result in the bullet disintegrating in mid air, it breaks up into pieces (assuming normal bullets, not tungsten core). That's why small arms ordinance typically doesn't go beyond ~3,000 ft/s.
Bullet drop is mostly an aiming challenge. The more a bullet drops, the higher you need to aim (or adjust the sights). For example 7.62x39 WP has a drop of ~40 inches (don't know the exact number) at 300 yards. However if you compensate for the drop by aiming higher, the bullet will hurt the target, no difference.
How much a bullet drops depends on its weight and the energy it has. Heavier and slower bullets will drop more.
The shape of the tip of the bullet will influence how much air resistance a bullet has. This is why hunting rounds are typically polymere (plastic) filled hollow points as you want good flight characteristics but destructive power at target. The plastic tip is no significant hinderance for hollow point expansion.
The shape of the nose of the bullet, the area immediately following the very tip, also determines air resistance. This "curvature" of the bullet is called ogive. This is why rifle bullets are shaped differently than handgun ammunition, because rifle bullets are designed to better deal with traveling through air over long distances.
The shape of the tail of the bullet will influence stability (wobble) and how well the projectile deals with "closing up the air" behind it, which is called drag. Basically the bullet makes a hole as it travels through the air which creates a (partial) vacuum at its end, which "pulls" the bullet back and slows it down. A boat tail design is typically used for long range high accuracy target engagement as the boat tail (look it up on Wiki) stabilizes the bullet and bleeds of drag well.
Let me know if you have questions.
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