Proposed change for range affect on damage

[mmartin798]

On page 88 of the 4th edition rules there is a section entitled "Range Effects on Damage" which outlines how E-factor diminishes with range. In short, the rule states that damage falls by 1 for every multiple of effective range. As is often the case, this didn't sound right, so I went to the spreadsheet and plotted the rule against the results from GNU Ballistics for three different rounds. The results are shown in the top picture entitled "Range vs EFactor-Current". The rule results are plotted in green while the GNU Ballistics results are in blue. It is pretty obvious that they do not match up very well. Also, contrary to the rest of text in the "Range Effects on Damage" section of the rules, the heavier rounds were not necessarily affected more. The lightest round in the sample was the 5.56mm. If you look the 9mm is much flatter than the 5.56mm showing the exact opposite of the regarding mass of the round. Fortunately this rule has a relatively easy fix, but to understand it, the GNU Ballistic plots need to be looked at in more depth.

If you look at both the 5.56x45mm and 12.7.99mm rounds, the pattern of the blue dots in both cases is very much a hockey stick. The 9x19mm is pretty flat. That is because the speed of sound is about 1100 f/s. That almost the initial velocity of the 9x19mm round. Looking at the 5.56x45mm and 12.7x99mm rounds the point where the curve flattens out happens around a velocity of 1100 f/s as well. From this we can assume that it is the faster than sound velocity that dramatically increases the drag. Again, comparing the 5.56 and 12.7 we see that the velocity drops to sub-sonic after about 2 multiples of the effective range and that the damage drops by about 1/3 of the range zero EFactor. This is a good start.

Looking at the 9x19mm plots, the rules drop off damage much too quickly. You get a much better fit if you drop the damage by 1 every 2 multiples of effective range.

Combining these two new findings to the rules column and plotting them against the GNU Ballistics result gives the results you see in the bottom picture entitled "Range vs EFactor-Proposed". These curves match up much better and the rules are still easy to apply.

[ArmySGT.]

How does it work out for cartridges that start out as subsonic? .45, .300, .458 SOCOM, black powder muzzle loaders; for example.

[mmartin798]

Originally Posted by ArmySGT.

How does it work out for cartridges that start out as subsonic? .45, .300, .458 SOCOM, black powder muzzle loaders; for example.

Without running additional ballistic plots, I would assume it runs like the 9x19mm, where the EFactor would drop off by 1 for every 2 multiples of effective range.


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[nuke11]

To "simplify" this, I started to provide range charts to the players for each of their weapons used.

I use a program called Ballistics Explorer v6.50 (an online site to use is http://www.shooterscalculator.com/).

Since we know the muzzle velocity of each weapon, I just find a cartridge that is approximate to the issued ammunition in the DB and plot a chart out to 1000 m for rifles/LMG, 1500 m for MMG, 2000 m for HMG and 200 m for pistols/SMG's at 50 m intervals.

They look similar to your Excel charts you show. I give distance, velocity, energy, time of flight and e-factor.

[mmartin798]

Originally Posted by nuke11

To "simplify" this, I started to provide range charts to the players for each of their weapons used.

I use a program called Ballistics Explorer v6.50 (an online site to use is http://www.shooterscalculator.com/).

Since we know the muzzle velocity of each weapon, I just find a cartridge that is approximate to the issued ammunition in the DB and plot a chart out to 1000 m for rifles/LMG, 1500 m for MMG, 2000 m for HMG and 200 m for pistols/SMG's at 50 m intervals.

They look similar to your Excel charts you show. I give distance, velocity, energy, time of flight and e-factor.

I considered this approach, like I did for whole body damage from explosives, but thought a separate chart for each weapon may not be as desirable as an algorithm.

[ArmySGT.]

What do you think of positive or negative to hit modifiers for range?

Bullet rise and the bullet drop haven't been incorporated into anyone's tables to my knowledge.

[nuke11]

MMARTIN798;

Did you ever finish this, or did I miss a file you provided?

[mmartin798]

You didn't miss anything. I just ran a sampling of ballistic plots to see if I could get an approximation using an algorithm of the actual results that matched up better than the overly simple rule in the book. I never did make an extensive spreadsheet of range charts. Though recently I have been considering it for use in a game aid. Basically laminated cards with a stat block, picture of the weapon, and a section to mark off rounds as you go with a dry or wet erase marker that would have the range card on the back. That also has not gotten beyond a basic mock-up of the card that needs revising.

[nuke11]

Originally Posted by mmartin798

You didn't miss anything. I just ran a sampling of ballistic plots to see if I could get an approximation using an algorithm of the actual results that matched up better than the overly simple rule in the book. I never did make an extensive spreadsheet of range charts. Though recently I have been considering it for use in a game aid. Basically laminated cards with a stat block, picture of the weapon, and a section to mark off rounds as you go with a dry or wet erase marker that would have the range card on the back. That also has not gotten beyond a basic mock-up of the card that needs revising.

Ok, I'll have to have a look and see what I can figure out.

I do like that idea of cards thou.

[mmartin798]

Hypothetically, if I were going to spend a few hours to generate the range charts for all the 4ed weapons, would it be safe to say all the pistols use G1 drag coefficient and all rifles use G7 drag coefficient? Otherwise, where would you suggest finding the appropriate coefficient to use? I would not use any atmospheric corrections, as those are way too situational.

[nuke11]

Originally Posted by mmartin798

Hypothetically, if I were going to spend a few hours to generate the range charts for all the 4ed weapons, would it be safe to say all the pistols use G1 drag coefficient and all rifles use G7 drag coefficient? Otherwise, where would you suggest finding the appropriate coefficient to use? I would not use any atmospheric corrections, as those are way too situational.

G1 for pistol is fine and G7 is fine for rifles. Most military rifle ball ammunition is boat tailed.

Using these will make short work on any calculations you perform.

[Desert Mariner]

Originally Posted by mmartin798

Hypothetically, if I were going to spend a few hours to generate the range charts for all the 4ed weapons, would it be safe to say all the pistols use G1 drag coefficient and all rifles use G7 drag coefficient? Otherwise, where would you suggest finding the appropriate coefficient to use? I would not use any atmospheric corrections, as those are way too situational.

The actual coefficients are normally listed on the box and/or in the manufacturer's literature. I started a similar exercise not too long ago and the first decision to be made is what specific cartridges to use. I ended up using cartridges from Sellier & Bellot (S&B) since they didn't have an overwhelming number and they provide the needed info (BC, V0 with test barrel length, projectile weight, etc.). Even this small selection provided 6 normal 9mm loads plus 2 subsonic 9s. I then computed the MV for each weapon with the selected cartridge. Picked an on-line calculator (Berger Bullets as it is simple) and set up an Excel sheet to import the generated data. The attached PDF is what I generated for 4E weapons (shotguns are not included as I'll need separate range charts for slug and shot).

Range cards for pistols run 10-200m at 10m increments, sub guns run 20-400m at 20m increments and rifles/MGs run 50-1000m at 50m increments. Some of these probably need adjustment. E-factor for each range is calculated from the listed velocity for the range. Cartridge used is listed on the range card as well so that anyone can recreate a chart at different ranges if they so desire.

I'm currently giving the same treatment to some updated weaponry but there doesn't seem to be much interest in the other thread I posted in.