t=937390
just for fun I did up a formula based system for popping HE Arty Shells on guys last year (hmm, year before?)... cause shelling folks is fun.
In a nutshell, for Artillery HE Shells
Take 1d8 for each 10mm bore
Drop 1d8 for each 5'sq the guy is from the point of impact
RefSave DC is 11+ #of dice (hmmm, was that it, or 15+... cant recall)
75mm PackHowitzer shell bursts with GuyA 15' away, and GuyB 25' away.
GuyA: 7d8 (75mm) -3d8 (15') = 4d8, Ref DC (11+ 4) = DC15
GuyB: 7d8 (75mm) -5d8 (25') = 2d8, Ref DC (11+ 2) = DC13
So the small guns aint so super deadly.... but do it again with a 155mm Shell:
GuyA: 15d8 (155m) -3d8 (15') = 12d8, RefDC (11+ 12) = DC23
GuyB: 15d8 (155mm) - 5d8 (25') = 10d8, RefDC (11+ 10) = DC21
GuyC: 15d8 (155mm) -12d8 (60') = 3d8 , RefDC (11+ 3) = DC14
so as you can see, the best way to survive a big arty shell is to not be next to it when it hits.... GuyC standing 60' away is in ok shape, but you dont wanna be the guy 15' from a 100lb shell going BANG!
Without using my formula,
in general, you should look at the Area / Radius of the shells you posted, and grow it so 20lb shells have bigger blasts than a hand grenade.
Also,
Consider the
Calliope Rockets as a salvo shot of AoE rather than single fired rockets. They shot a volley of rockets to saturate an area in an almost shotgun plan: If one rocket will hit somewhere in that general area, then fire 12,24,60 rockets to hit everywhere in that general area. In our terms, treat it like a super Autofire-esque AoE,
12Rocket Shot, 60x60', 4d8 Ref DC20
Add 12 more rockets for +10'r, Or +2d8, Or +3DC, or EvasionProof, one choice per additional set of 12
---this is from the hip, if you like it you can run with it for the details & math
<note: source put the 4.5" rocket on par with 105mm shell for Bang!>
I do like you formed a plan with ATGuns & Arty done with what appears to be a rule of thumb compared to the Tankguns. I like formulas & guides rather than having to make up every possible gun
I think it's a real cool rule, but how would you explain the M3 L/40 (75mm) being so inferior to the KwK (75mm) or to the 17-pounder (76,2mm)?
Additionally, I would find it a bit underpowered if a direct hit from a 20mm Antitank gun would deal the same amount of damage as a standard rifle. Should it then have a very high Armor Penetration (e.g. ignores 5 points of Hardness)?
If you shoot a 20mm HE shell at a 5'square as 'shelling' then the formula might be used, but the non-linear nature of d20 makes the extremes of the formula lose accuracy. 20mmHE does a bad job of maybe hurting 2 or 3 guys in an area attack, but a great job of killing the heck out of a guy you aimed specificly at & hit in the chest.
0' : 2d8 (20mm) -0d8 (0') = 2d8 , RefDC 13
5' : 2d8 (20mm) -1d8 (5') = 1d8 , RefDC 12
which does a decent job of showing why we dont shell big areas with single 20mm cannonfire, it is horrible at that task due to tiny warhead loads. However, blast out an area Autofire-esque (BarageFire?) 20x40' 2d8 DC18 Vulcan 50rnds 20mm HE and you get better results
PointTarget direct fire 20mm HE would do the 2d20 (3d12/4d8 whatever you use at your house) to the target object/guy it hit
The velocity/power of the cannon has little impact on the shellburst from similar bores: lobbing a 20lb 105mm shell 300y or 3000y is still the same 20lb bomb going off next to guys in the target area. So a 60mm mortar would have similar hurtfullness on guys 400y as a 57mm gun shell hurting guys 1500y away.... the distance the shell traveled(or time it took to do it) before hitting the ground 15' from a guy dont matter.
As for similar gun comparison,
a) d20 Coarseness can cover up a lot of fudging numbers
b) Range Incs make better guns better at hitting DirectFire (& area too)
Consider a 3" 120'RI gun vs a 160'RI gun at 500' Targets: -10Tohit vs -6Tohit
c) Direct Fire & AP can use the different power levels of different guns, the 17lb'er can have a die or 2(or more) more damage on point targets than the 76Tankgun. This also is where you can look at fuzing options: 16" Navalgun AP punched 30" of steel, then after that the explosives inside went bang.
The RAW standard, of folks being just as hurt at the end of the explosion as the guys at the center, makes statting radiuses hard, lest you end up with 10" Navalgun shells with 20d12 but yet only 25' radius because it would be extreme TPK to do 20d12 90'r DC25 and folly to nerf it down to 8d6 90'r DC15 to the guy it landed between his feet. So picking radius numbers is hard work in RAW
---
In reply to a PM I got asking about the AT Guns
Take a nice little AT Gun like the 57mm.
It shot (US) only AP / APC(AT) as general issue <Armor Piercing Cap- hardened cap solid slug>. The Brits 6Pounder ammo was usable in the gun, and they had HE as well to make the gun more versitle in the field. But lets focus on the AP- it is a bullet, a KE Penetrator, and should be treated in game as a bullet.
The larger AT guns also had AP/APC(AT), and HE shell, but APCBC as well which had a small BurstCharge as well. This is by no means a HE shell, more like the games Explosive Ammo for AK/m16/firearms that just gives a little more damage as a bullet attack.
In many cases, the added Umph the AT Gun got over the TankGun of similar caliber is that the AT Gun would have a longer barrel for better KE Penetrator power
So if I take the 10mm Bore = 1d8 rule, add High Explosive to the ammo as well as Armor Piercing (we use a slightly different AP rule, it ignores Hardness or DR [we use DR to armor]), but cut off the artillery blast radius rule, it should be appropriate?
But this doesn't explain why the 75mm of a M4 Sherman was so lousy compared to the 76.2mm of a M10 Wolverine. I recon the 75mm should deal 7d8+HE+AP, and the 76.2mm would deal 8d8+HE+AP, but is that a significant enough damage difference?
Sherman 75mm L40 tankgun velocity with AP slug is amost 600m/s
Wolverine 76mm L50/55 ATgun (3") with heavier AP slug is almost 800m/s
rules... Lets see... Just gonna throw some ideas out & see how they fit
Cannons >40 : 1d8 damage per 10mm bore
AP solids: as Cannon, plus 1 point Ignore DR/Hard/Def(?)
APCBC burst: as AP, +1 Fire damage per bore
AT Guns : As above, +2 damage per bore
HE Shells : by shelling formula for bore vs distance
so
75mm AP Tankgun: 7d8(bore) + Ignore7(AP)
57mm AP ATgun: 6d8(bore) +6(ATgun) + Ignore6(AP)
88mm APbc Tankgun: 9d8(bore) +9Fire(bc) +Ignore9(AP)
17lb'er APbc ATgun: 8d8(bore) +8(ATgun) +8Fire(bc) + Ignore8(AP)
It sounds good. It's real nice to have someone who knows a lot about the subject here. I appreciate it, thanks.
/Thomas
no problemo-
Its not that I memorized ever cannon stat since the 1300s,
I just have some decent GoogleFu and a set of nice links, such as
Navweaps.com for weights & velocities
I'd love to see weapons and AdC's/PrC's... This vehicle and artillery stuff is a bit too hardcore maths for me; the discussion especially...
Not to worry,
the technical discussion is just to generate the stat numbers. Once the method of statting is found, then the end users (gamers) just use the shopping list of guns/vehicles with regular stat blocks