Sabot range for modern autocannons

[dmnt]

It all started rather simple, going over Bushmaster 30mm Mk44 AC statistics and I had 3 references that said "over 100 mm @ 1000m 0deg." I also encountered 40mm BM and Bofors stats including muzzle velocity, travel time etc. and being what I am (computational science minor), I started digging in. So all the physics aside, I made a simplistic assumption that gravity doesn't matter to vertical speed (it does, but not much at these speeds/ranges) and came up with some fancy equations without an exact solution. Unanswered questions remained, like "is the armor penetration depending more on the momentum (velocity x mass) or the kinetic energy (½ x mass x velocity x velocity)?"

After 5 a4 papers with equations and some coding, here's the php scripts that I made:
First:
round velocity and distance (plus penetration capability as percentage of point blank range both for momentum and energy) by time, given the muzzle velocity and drag constant*) for type of ammo: http://www.venhola.com/winspmbt/sabotcalc.php

Second:
Estimate the drag constant for ammo given the muzzle velocity and flight time to distance:
http://www.venhola.com/winspmbt/sabotcalc2.php

You can use the second to estimate the value for the first and to get penetration estimates at given flight times. Unfortunately not yet for distances.

What I suspected was that the penetration capability is dependent both on the momentum (which dictates the impact peak force) and energy (which is reduced on impact due to changing form of armor) and at least for Bushmaster 30mm Mk44 AC it was almost 100% match using 50:50 division between them, so I added the 50:50 mix to the lot. I was using this data as a reference as it reflected pretty much the penetration in OOBs for 30mm BM Mk44 (120 mm @ 0m 0deg vs. approx 62 mm @ 0m 60deg).

As an example, 40mm Bofors AC - used in Swedish CV9040 - has been given table values "Muzzle v: 1.48 km/s flight time to 1.5 km = 1.1 s". The 2nd link gives us a constant c = -0.10773241083846 (last iteration result) which we feed to first. As a result for flight time 1.1s it gives:

t: 1.10s v: 1.26 km/s dist: 1.50 km momentum: 85.1% energy: 72.4 % combined: 78.7%

Suggestion there is that penetration at 1500m should be 78.7% of 0m penetration 200mm, 200 x .787 = 157.4 mm
Army-guide.com tells us "At a tactical firing range the penetrator can penetrate armor well in excess of 150 mm."
"When firing against armoured vehicles the maximum upper range bracket is between 1500 and 2000m" (The Bofors Gun, Terry Gander)
at 2km it is 72.9% or 146mm, which is again well within scope.

The problem with sabot ammo is naturally that after given range the accuracy and efficacy drops, but is the sabot range in OOBs there to keep the game balanced (sacrifice some penetration value realism for tactical realism = "don't be trigger happy @ 3km ranges") or is the sabot ranges for modern autocannons close to gun max ranges because they just used to be about the same for MBT guns? Judging from this pic the 30mm Bushmaster should have Sabot Range set somewhere 150 hexes...

*) drag constant here is in physics POV "½ x density of air x cross-surface area x C", where C is between 0 and 1 and depends on the form of the object. However, one number is enough for us.

[Suhiir]

Ummm ... while a LOT of real world data is used in the game a fair number of things are also generalized for play balance. Weapon ranges often being one of them. An X caliber weapon fires Y distance. Not totally accurate/realistic but in the ballpark and pretty standard across all OOB's.

[dmnt]

Sure, I get that. During the years I've learned a lot on the middle ground between reality and the game balance. Weapon ranges are effective ranges to moving targets, not "fire at 40 degree angle and shot will land there" ranges.

As far as I know the sabot penetration in the game is linearly dependent on target distance but that it is not sabot_pen * (1 - distance / sabot_range), i.e. it's not sabot_pen at zero distance and 0 at sabot_range distance. From what it looks like in 30mm Bushmaster Mk44 is that it goes to 0 at around 1.5 times the max distance or so:
pen(distance) = sabot_pen * (1 - distance / sabot_range / 1.5).

Am I correct in my assumption that a longer sabot range does not allow firing at that range? The Mobhack manual does not state that definitely:

(If the sabot round has the same AP value as the AP shot, but longer range, the draw down for range will be less for that round at any range X as opposed to the shorter ranged AP shot, so the longer ranged sabot round will penetrate more armour at any given range X). (The draw down decrement for range is roughly linear.)

Also, if the fact is that the system is designed (and consistent between OOBs and weapons) to be a bit underpowered at longer distances (beyond 1km) then I'll have no problem with that and I will be more enlightened after learning that fact.

[shahadi]

Originally Posted by dmnt

Sure, I get that. During the years I've learned a lot on the middle ground between reality and the game balance. Weapon ranges are effective ranges to moving targets, not "fire at 40 degree angle and shot will land there" ranges.

As far as I know the sabot penetration in the game is linearly dependent on target distance.

It's been too long since my Calc classes, therefore, allow me a wee bit of latitude here. Is it fair to say, the game calculates trajectories internally, the player need not elevate a weapon to fire, simply id target, and account for range and ammo type. Therefore, to the player the fires are linear, although internally the game calculates a trajectory.

After reading this thread several times, I loaded the tutorial scenario, slot 000, engaged an Iraqi tank to document what the game reports at point of impact with the following:

Please note the following values: Pen 109 (HellFire missile) Arm 21 (armor rating of T-55), @15 degrees (angle of Hellfire impact).

Now, loading up Mobhack, I find the Hull Front Armor value for the T-55QM is 20, and the HEAT Penetration values for the Hellfire A is 105.

If the game targeting is simply linear, why the angle of Hellfire impact value is reported?

So, please excuse if I've completely missed the point here, I just found the article fascinating to the point that I felt compelled to contribute my "two cents worth."

And, if someone would explain the variance in the Armor Hull, and Hellfire HEAT penetration values, as reported in MobHack and in game play, I'd be a happy camper.

[Mobhack]

If you want to play with new values effects then simply edit a copy of the weapon in Mobhack and then use apcalc to view the new results. The help is in a text file called armourcalc_help.txt - read it!.

I usually copy the original weapon to a free bit of space in the weapons list, then copy the new one under it from the original as well. That saves having to scroll about to find things for comparisons. Retitle to something like TEST 001 so its easy to find and to kill it later, when done with testing.

The MBT_ or WW2_APcalc utilities live in your home game directory.

NB - the utility is not 'live' - so close it and reopen it to load any changes you make in mobhack.

[dmnt]

Originally Posted by Mobhack

If you want to play with new values effects then simply edit a copy of the weapon in Mobhack and then use apcalc to view the new results. The help is in a text file called armourcalc_help.txt - read it!.

I usually copy the original weapon to a free bit of space in the weapons list, then copy the new one under it from the original as well. That saves having to scroll about to find things for comparisons. Retitle to something like TEST 001 so its easy to find and to kill it later, when done with testing.

The MBT_ or WW2_APcalc utilities live in your home game directory.

NB - the utility is not 'live' - so close it and reopen it to load any changes you make in mobhack.

Thanks, I've already tried and tested that before drawing any conclusions. I was a bit unclear on the "sabot linear range", what I meant was that the sabot penetration depends linearly on the distance. Using MBT_APCalc.exe I pretty much drew this conclusion thru series of tests.

Still the unanswered big question I'm having is that is the sabot penetration deviation from real world tests a game balance design issue or is it that recent technological advances in APFSDS ammo have not yet been carried to the game? (Or 3rd option: something completely different)

I'm trying to gather more data about different guns and ammo types just to dig to the bottom of this. However, lack of public data is a hindrance.

[Mobhack]

You wont be told anything about the formulae since they are proprietary to SSI and not to be revealed (part of the agreement when the code was released).

Therefore - its up to you to figure it out as to how it fits your expectations.

As to public data - all lies and and manufacturers advertising. hard data is difficult enough to find for WW2 era ammo, and modern stuff is current and hence classified.

[DRG]

The entire exercise is pointless . These are direct fire weapons . The maximum range for direct fire weapons in the game is 99 hexes max because 99 is the max visibility of the game and that isn't ever going to change and for probably >99% of the generated games the visibility will be UNDER the max range of any tank / IFV weapon in the game anyway so the question has to be asked.... what's the point of saying "the 30mm Bushmaster should have Sabot Range set somewhere 150 hexes" when that's 51 hexes further than you can set the games visibility ? All ranges >99 for direct fire weapons are pointless ( yes, there are lots and all pointless because 99 is the max visibility that can be set and therefore the max range you can shoot them )

There's a similar issue with aircraft weapons ranges...... aside from standoff weapons the nominal 40 hexes a lot of aircraft weapons get amount to eyecandy because aircraft in the game only ever engage targets at < 1/4 that range

[dmnt]

One of the questions in the very first post condensed into one sentence:
Is the maximum range for a gun to shoot sabot rounds the actual "range" value even if "sabot range" is greater?

Another quick question still unanswered:
Is the low penetration at ranges longer than 10 hexes a game balance issue or OOB data issue?

My main issue here is the deviance from real world penetration values in usable ranges, between 20 hexes to 40 hexes and using sabot range adjustments for fixing that (the way sabot range adjustment has usually been used to decrease the effectiveness).

As for the formulae I do know that they're the trade secret yet we can check the outcomes using mbt_apcalc for example. Or setting up a gazillion scenarios and write down the results of our shots.

Of course manufacturers put up the results they have gotten when shooting in the perfect conditions with pre-warmed rounds in low atmospheric pressure and brand new barrels targeting 2nd grade RHA targets. And different testers get different results. Still we get the ballpark figures over there.

[DRG]

APCalc uses the games code to show penetration values so running tests at various ranges and comparing them to whatever source you trust will give you the answer about how close we are to whatever penetration reality they are claiming their weapons will do. REMEMBER there are a HOST of variables that effect penetration so you need to run the tests a good dozen times to see the highs and lows but APCALC only deals with normal penetration variables not the random factors the game throws in after the fact and when all is said and done I'm not going to change any data unless more than one source proves we have incorrect values so I'm not the least bit interested in theoretical penetration of say..... 8cm at 2000 meters when it works out to 7 or 9 in APCalc show me we are grossly out and I'll pay attention