Greetings all. I've been familiarizing myself with the advanced explosive rules in Arsenal, and I've run into an issue. First off, let me quote a few relevant pieces of text:



Makes sense, but I can't get it to work out in practice.

Okay, lets say we are faced with a security door. That counts as Reinforced Material, so we have Structure Rating of 9, and an Armor Rating of 8.

Let's also say that we have a drone carrying 200 foam explosive canisters, each packed with 1 kilogram of Rating 4 foam explosive.


So if we decide to breach the door, lets figure out how much explosive it's going to take.

Arsenal gives us the following:

DV required = (Radius[m] x Structure Rating) + (Armor Rating ÷ 4)
Explosive weight = (DV ÷ DV Multiplier ÷ Explosives Rating)squared in kg

So to blow a 1 meter diameter hole, we need a DV of
(.5 * 9) + (8 / 4)
(4.5) + (2)
6.5 or 7 DV

Let's say we are just putting the explosives on the ground, so the Multiplier is x1.

The weight in kilograms is:
(7 / 1 / 4) squared kilograms
3 kilograms

So 3 kilos of rating 4 foam explosive will put a 1 meter diameter hole in our security door.

Good 'nuff.


So let's say instead of breaching it, we decide to try cutting it.

We are going to attempt to cut a 1 square meter hole out of the door.

We are still using rating 4 foam explosive, and we will shape it into four 1-meter lines.

The DV formula for cutting is: (sqrt of kilos/meter)*(Rating of explosives)
We also get 1 additional AP per net hit made on the demo extended test (assume no net hits, so no AP)

The door can buy 2 hits from it's armor, effectively giving it 11 damage boxes.

If we want to do 11 boxes of damage, we will need almost 9 KILOGRAMS PER ONE METER LINE!!!
DV = (sqrt 9)*(4)
DV = (3)*(4)
DV = 12

Holy shit. You need a grand total of 36 kilograms of the same explosive to cut a 1meter square hole out of that security door, whereas you only need 3 kilos to blow a 1meter diameter hole. WTF???

Please tell me my math is wrong...

[edit]
My math WAS wrong, so I fixed it. But all the correction did was change the required mass of the breaching charge from 5 kilos to 3, exacerbating the problem with the cutting charge calculation.
[/edit]

You half a target's armor when the explosive is attached directly to is (SR4 p. 315) and why the hell do you have 0 net hits? If you're going to do it keep making the extended test until you have so many hits that it doesn't matter anymore. Also remember that Each net hit adds to the explosive's DV.

A couple of things. First, the demo rules in Arsenal supersede the demo rules in the BBB. In Arsenal, net hits on the "Cutting" explosives test only add to the AP rating of the explosive. Secondly, even if you get enough hits to ignore all the targets armor in the above case, you STILL need each meter-long strip of explosives to do 9DV to cut through the Reinforced Material (Structure Rating 9). According to Arsenal, the DV for a cutting attempt is computed as follows:

DV = (sqrt of kilos/meter)*(Rating of explosives)

So for the above door, even if you generate enough successes to ignore the armor entirely, you either need a single kilo of rating 9 foam explosive, 4 kilos of rating 5, or 9 kilos of rating 4 PER LINEAR METER.

Like I said, either my math is wrong, or something is very wonky with the advanced demo rules in Arsenal.

The demolition rules in Arsenal don't supersede the original rules; they add to the original rules.

I agree with hyzmarca, the Arsenal explosive rules enhance or add to the ones in the BBB.

WMS

When it comes to breaching, they change the way damage to a barrier is calculated.




So the mechanic of the skill test net hits added to DV don't really apply. Or, at least, don't apply when determining how much damage the explosives actually do to the structure you are trying to breach.

With the advanced rules, the GM rolls the skill test, with modifiers based on how much intel the demolitionist has about what he is trying to breach. The results determine the quantity of explosive that the demo guy THINKS he/she needs to do the job properly. The actual value may be more or less, depending upon the number of hits scored.

With Cutting Charges, the rules change yet again:



Again, there doesn't seem to room in these rules to allow for "net hits add to DV" or "use 1/2 armor if explosives are placed against a structure".

It doesn't say you don't and if it doesn't say you don't then you do.

Indeed. Can you give me an example of how the Cutting rules work with the explosive rules from the BBB?

Its simple. For cutting when the explosive is placed directly on the surface total DV = [ √((mass in kilograms)/distance in meters)]*(Rating)] + (Net Hits) and AP = [(-half) + (net hits)]

This, with say 4 net hits a the explosives expert totally negates the door's armor and is able to cut it with only one kilogram of rating 5 per meter or (5/4)^2 of rating 4 per meter.

Now, to create a circular hole 1 meter in diameter you only need a curve line π meters in length of the actual requirement is (25/16)π kilograms for rating 4 foam. This is slightly more than the breaching change but can be further reduced by spending time to get more net hits.

With 5 nets hits you only need π kilograms of rating 4 to cut the hole and with 6 net hits you only need (9/16)π kilograms of rating 4 to cut he hole.

It does not say in the Cutting section that Net Hits add to the DV, and thus they do not. It is false unless stated otherwise, not vice-versa.

I reject your reality and substitute my own!





Cutting is better for making holes of less than a a decimeter. I think. The problem is that when making calculations for a circular cut of a decimeter in diameter the explosives DV is the square root of a variable times the product of two irrational numbers divided by the square root of a transcendental number. Breaching is still better at 1 decimeter (29/40 kilos vs 81π/160) but cutting is better at 1 centimeter is diameter (209/400 kilos vs 81π/1600 kilos). Yeah, without extra DV cutting sucks.

Yeah, that's sorta what I was trying to get at. In my mind, it should take less explosive to cut a 1 square meter hole in a given material than it does to just breach a 1 meter diameter hole. However, it should take a lot more time to setup the cutting charges, since all breaching takes is slapping the explosive on the surface and pressing the "detonate" button on your commlink.

It would make sense that way, and I even believe that is how the devs intended it to work, but the mechanics just don't deliver that.

And I should point out that even if you use the following explosive rules from the BBB, breaching is STILL more efficient than cutting, which doesn't really make sense.

1. Hits on demo test add to effective rating of explosives
2. DV is doubled vs. barriers
3. Barrier rolls armor (instead of double armor) to resist when explosives placed on the surface of the barrier.

If those rules apply to cutting, they apply to breaching too.


One possible fix is to have the net hits on the Cutting Demo test either add directly to DV, or to function as a multiplier to DV. That would make cutting a much more efficient option when you have the time to do it.

Is it just me or is the entire amount of explosives needed in SR4 completely wonky?

Considering how powerful explosives are today not much difference should be made in 60 years.

I mean, really, would it really require KILOGRAMS of explosives to make a hole in a wall or could it be 1/10 of kilograms used. Instead of using kilograms you split the amount by 10.

Or is it that the explosives rating goes from firecracker strength at rating 1-2 and commercial at 3-4 and above that you get into special equipment strength and military applications.

I just find the amount of explosives needed a bit excessive.

Can you imagine the death and destruction you could cause with a simple fireworks display gone wrong? I mean those are some huge rockets and mortar balls that pack a lot of BOOM!

I've been spending time talking to a guy I work with who used to be an Engineer Sergeant in the 19th Special Forces Group. According to him, you DO need a metric shit-ton of explosives to breach walls if the charges aren't tamped. That's probably why the explosives rules in Arsenal give DV multipliers for properly tamped demo charges. Of course, the better your setup, the smaller quantity of explosives you need to do the job effectively.

When I was playing with the numbers, I found that commercially available explosives (rating 3) are extremely powerful, especially if you are using them to breach something that is underwater, or if you are able to properly tamp them.

One issue is that, in real life, explosives obey the inverse-square law for heat and the inverse-cube law for shockwaves, meaning that power drops exponentially with distance. In SR, power drop linearly with distance.

I can only hope that the rules for cutting with explosives have left something out.

The problem is that they aren't boosting the power of the explosives when you're 'cutting'. So, you need to do more DV, which requires that you use far more explosives because the ratio of DV to kilogram is a squared value.

Just use this to calculate the amount of explosives while cutting:

DV required = (Barrier Thickness[m] x Structure Rating) + (Armor Rating ÷ 4)
Explosive weight = (DV ÷ DV Multiplier ÷ Explosives Rating)squared in kg (per 1 meter)

So, if I assume that our SR 9, AR 8 door is 10 cm (.1 m) thick then:

(.1 x 9) + (8 ÷ 4) = 2.9 or 3 DV.
Thus, Explosive weight = (3 ÷ 1 ÷ 4)squared = 0.5625 kg of explosives per meter. So, given a square with 1 meter sides, that would be 2.25 kg of explosives in total. That's better than 3 kg for a 1 meter circular hole.

If you want to compare them accurately, to cut a 1 meter diameter hole in the door would take Pi * 0.5625 kg or 1.77 kg of explosives. So, you'd use a little over half of the amount of explosives to cut via this method.

I suppose that could work. Still, I'd like to see some official word on how it's supposed to work. Especially since I'm about to be a former SBS Underwater Demo expert in an upcoming game.

So that's it? No one else has any more info about the explosives rules in Arsenal?

Has anyone used them, or any GMs had a player use them in their games?

OneRonin: I reread the rules for breaching/cutting and I think you're right- there is something a little off about the amount of standard explosives.

Have you done the calculations using the linear cutting charges? Maybe the rules were written with those in mind, though it seems odd that cutting charges are always considered untamped. When you read the description of the cutting charges it sound like they have built in tamping (the angled iron that "focuses the explosive blast onto the line to be cut"). Anyway that -5 AP will make some difference, but not enough to correct the massive amounts of explosives you need for cutting. Doesn't make much sense.

One thing I noticed was the note about rubble obscuring up to half of the hole you create with breaching. It gives the impression that breaching is a really messy affair, but cutting has no such rule. Maybe that is one distinct advantage to cutting but I don't know if thats worth the extra explosives either.

As far as the rules in Arsenal superseding the rules in the BBB- my interpretation was that the multiplier from the Positioning Table on page 90 basically replaces the "DV x 2 against barriers" from the BBB. In other words the BBB assumes that all charges are placed "Higher above ground than hole radius, untamped" (x2) for the sake of simplicity.

Even if you switch to the cutting charges, the problem remains. Let's suppose that you've managed to get 3 successes on the demo extended test and have gained -8 AP. You would now need a DV of 9 instead of a DV of 11.

So:

DV = sqr(kg) x r
OR
9 = sqr(k) x 4
k = (9/4)^2
Which means that you need 5.0625 kg per meter.

If you're being generous, that would mean that you'd rap the linear cutting charges around the hole 5 times, for 20 meters and 20 kilograms of explosives. Of course, technically, that's a bit shy of what's actually needed, so cruel GM's would make you wrap it around 6 times for 24 kilograms of explosives.

Now, say that you took that same linear cutting charge as a breaching charge. The calculation would be almost the same as before, except that the armor on the door drops by 5.

(.5 * 9) + (3 / 4)
(4.5) + (.75)
5.25 or 6 DV

So, you need 6 DV to create a 1 meter wide hole.

6/1/4 = 1.5
1.5^2 = 2.25 kg

2.25 kg is a lot smaller than 20-24 kilograms.

So, um, yeah. There's a hole in the explosives rules.

How about this? Let's treat linear cutting charge DV just like breaching DV, and assume that they automatically get the x3 DV multiplier for being above the ground and tamped. So we end up with the following math:

The DV formula for cutting is: (sqrt of kilos/meter)*(Rating of explosives) *(DV multiplier for above ground + tamped)
We also get 1 additional AP per net hit made on the demo extended test (assume no net hits, so no extra AP)
Base AP for Linear Cutting Charges is -5 AP

So the lowest rating linear cutting charge you can get is rating 4. And there is 1kg of explosives per meter.

So we have: (1)*(4)*(3) = 12DV. Our sec door has Armor 8 and Structure 9. With the -5AP from using a linear cutting charge, the door doesn't have enough dice to buy any hits, and our 12DV is more than enough to cut it. Of course, we do end up using 4kg of explosives, but that's not too bad.

If the cutting charges only had .56kg of explosives per meter, then we would come out RIGHT at 9DV. And we do it with a little over 2kg of explosives rather than 4. I could live with that.

So here are some sample numbers for cutting when using the 1kg linear cutting charges from arsenal, and assuming the x3 DV:


Heavy Material: Armor: 6 Struct: 7
Example: hardwood, dataterm, lightpost, chain link
*Rating 4 charges will do the job easily


Reinforced Material: Armor: 8 Struct: 9
Example: densiplast, security door, armored glass, Kevlar wallboard
*Rating 4 charges will do the job easily


Structural Material: Armor: 12 Struct: 11
Example: brick, plascrete
*Rating 4 with just barely do the job. 4 or more net hits on your demo test will guarantee it.


Heavy Structural Material: Armor: 16 Struct: 13
Example: concrete, metal beam
*Rating 5 will just barely do the job. 4 or more net hits on your demo test will guarantee it.


Armored/Reinforced Material: Armor: 24 Struct: 15
Example: reinforced concrete
*Rating 6 will work only if you get 4 or more hits on your demo test. Otherwise, you will need rating 7.


Hardened Material: Armor: 32+ Struct: 17+
Example: blast bunkers
*Rating 8 will work only if you get 4 or more hits on your demo test. Otherwise you will need rating 9.



That works for me.

So, is the consensus that cutting is meant to be accomplished by cutting charges?

Well, according to Arsenal, you can use just about any sort of explosive for cutting. However, the Linear Cutting Charges in book are designed specifically for cutting, and automatically start with a -5AP, in addition to however many net hits you make on your demo test when setting them up. This assumes you are cutting holes into a relatively large and flat surface. I would imagine that meter-long LCCs wouldn't work very well if you are trying to cut something like a 10-inch diameter round concrete pillar.


Technically, you should be able to use foam/plastic explosive to cut as well, but should be considerably less effective than the LCCs. Though the rules as written in Arsenal don't really reflect that.


IRL, you can even cut with det cord, though the amount of explosives listed in det cord is so small that you need about 10 meters of it to do 2-3 DV, which is retarded. Though I haven't figured out how to better handle it. Det cord might work better with a set DV/meter rather than basing it of the mass of explosives.

There are two ways of using explosives to cut steel. You can blast cut steel, or you can cut it with a shaped charge. Blast cutting steel requires quite a bit more explosives than using a shaped charge, but making effective shaped charges, particularly things like linear and flexible linear shaped charges requires quite a bit of skill and they are usually factory made.

There are various techniques for blast cutting steel and they are adapted to different targets. Typically if you have the and target info time to build the proper explosive change you can do things like build ribbon charges that will blast cut it with much less explosives than needed for brute force solutions. It's still more explosive and weight than you need for a linear shaped charge.

To fiddle with the rules and verify the accuracy you'd have to sit down with a copy FM 5-25 or a good text on explosives and run some numbers, then convert them into SR terms.

The other issue you run into in real life is that you apparently can't blast cut some metals, like Nickel-Molybdenum steels.

Or for instance in Arsenal we could use a shit load of ammonium nitrate based explosives to destroy heavily reinforced targets, where as in real life it won't crack a slab of steel reinforced concrete no matter how much explosive you pack on. The velocity of the actual explosion which is determined by the type of explosive, is the principal means of determining what type of explosive to use on particular materials.

I also agree on the detcord issue, great shit for cutting down trees

The Oklahoma City Federal Building, many IFVs, Humvees, and other vehicles all beg to differ, yo. With enough Ammonium Nitrate, you can blow up just about anything. This is true of any explosive.

That is simply wrong. What happened in OKC was that the charge destroyed or displaced columns G16, G20 and G24, resulting in the 3rd floor transfer girder failing, which brought down the floor slabs above it.

A light armored vehicle is a collection of parts bolted or welded together. If you use a large enough charge you can cause the joints to fail. If you use a sufficiently large charge you can toss the entire vehicle into the air and kill everyone inside. You will not actually produce a hole in the armor plate, though you might deform the vehicle structure such that you get blast wave entrance into the vehicle. For example, blowing in the windows. However, the use of ammonium nitrate in Iraq is unusual, as IEDs and factory produced mines are almost always filled with TNT or other high explosives that have a much higher detonation velocity.

Do not forget The Texas City Accident
Texas City Disaster

Many Steel Reinforced Concrete Structures were blown away in that one. Check your number/ facts. Get your noses out of the text books and get some RL experience.

kansas City

Ammonium Nitrate Explosion in Ryongchon Train Station

Chemical Plant Explosion

Cause of the Port Neal ammonium nitrate plant explosion

Explosion in a urea ammonium nitrate (UAN) fertiliser transfer pump

WMS

Correct me if I am wrong but where not those columns made of reinforced concrete?

WMS

Before you go telling me I am wrong please try to know something about what you are talking about. Most ammonium nitrate suicide bombers are using that as a basis for anti personnel damage, however they normally use a TNT booster for causing greater damage to structures and vehicles. RDX, PETN, HMX are preferred if available (principally RDX the other two are more specialized). The Oklahoma City bombing was surrounded by conjecture and conspiracy theory precisely because of the damage inflicted by what was supposedly a pure ammonium nitrate bomb. According to the court records traces of RDX was found at the OKC site. The conspiracy theories arose from assoreted government agencies attempting to cover up the fact that restricted high explosives had in fact been used. How they came to obtain it, and the weaknesses in the USA's regulation process were undoubtedly buried as part of national security (hello mr. terrorist dont bother smuggling it in you can just buy it here!) and a large measure of CYA. OKC was a huge embarrassment to the ATF precisely because they are responsible for keeping restricted explosives out of the hands of lunatics.

Lastly for your information I have done my fair share of demolition, and the explosive velocity vs. appropriate demolition targets is basically Demo 101.

KZT nice to see someone who has a clue.

WearzManySkins none of the articles you pointed out prove a thing. None of them have anything resembling actual composition of the targets. I can pretty much gurantee you most of the damage was from soil displacement and gravity. Also if you ever spent anytime overseas especially in what was the Communist Block (and yes North Korea uses similar construction techniques) you would realize that 90% of industrial and residential buildings are actually constructed of unreinforced cement block, which last time I checked is not real resistant to a sledgehammer much less any kind of explosive. Lastly my knowledge is text book and field.

Yup. They failed in two ways, shear and brisance. In G20 the concrete was essentially blown apart as it was quite close to the truck (in the 10,000 PSI zone), the other two failed when overloaded, I think by the blast wave.

What happened under blast load on G20 is that the concrete is shattered and displaced, and the bent but uncut steel rebar collapses under the load of the rest of the building (as rebar isn't designed to be load bearing in compression). You can't cut reasonably thick steel with AnFo. You can bend it, you can shatter the backing and hence displace it, and you can fracture the joints, but it won't be directly penetrated by the blast itself.

...this is where i miss the old complementary knowledge skill roll.

Not Anfo but the Port Chicago blast sheared off a concrete reinforced ammunition handling pier. The remains were visible for a long time.

Merely because you do not see any buildings of reinforced concrete does not mean any where not there. Records of buildings at those location may still be around.

WMS

Probably because the Port Chicago blast was the result of mishandling of MILITARY MUNITIONS not ammonium nitrate.

OK your statement above emphasis mine, you stated that no amount of Anfo will crack a slap of concrete.

As what KZT has posted several the columns were "cracked" by the explosion, as for how the building was brought down is secondary. As to what exactly caused the "Cracking" is immaterial. Your statement above about not "cracking". You did not state blow a hole in it. If you had this discussion would have taken a different turn.

I did not talk of Terrorist explosions or events in contested war zone. I was proving your above state to be inaccurate at best.

Only one of the links I listed was in a Third Word Country, I will concede that NK has poor construction standards.

But in all of those listed explosions there were are reinforced concrete, the evidence by the blast is gone or been removed by reconstruction. But the piers in the Texas City and Port Chicago explosions were made of reinforced concrete, maybe not up to days standards but by the standards of then yes. Tell me how soil erosion took away those piers?

I am merely proving reinforced concrete can be "Cracked" by a explosion of Anfo.

WMS

You miss my point, the Blast sheared off a reinforced concrete pier at the water line, I as also stated not Anfo.

WMS

Misunderstood what Ampo was probably because it is not a term generally used to reference ammonium nitrate (unless you are looking for ANFO), which is what we were discussing. We were discussing ammonium nitrate so the fact that military munitions (of which very few are ammonium nitraete based) caused that kind of damage is not surprising.

Additionally when I said crack more accurately I should have said shatter, or break. The brisance of ammonium nitrate is insufficent in itself to crack or break or shatter steel reinforced concrete. Damage can still occur due to other factors of the explosion, such as what is the target resting on, what are supporting structures made of and how are they supported. Is the reinforcement continuous or not. If I have enough explosive to level everything in a 500m radius a lot of the damage will result from the shockwave both in the air and through the ground displacing supporting material (earth or unreinforced materials) or by applying force in a direction from which the materials are not reinforced resulting in displacement, at which point gravity takes over inflicting the actual damage. The end damage is not what I was referring to.

"Look Seaman Recruit Nelson is the light on or off, pike your electron flow lectures techno babble."

WMS

Typical concrete is about 3000 PSI strength in compression, good concrete up to 5000 PSI. At 10,000 PSI pressure the concrete internally fails, irrespective of what produces the pressure. The steel rebar will not be broken by this, but most of the compressive strength in a reinforced concrete structure is from the concrete. You apparently get similar effects with using HE or small arms to mouse hole breach a reinforced concrete wall, in that you blow a hole in the concrete but the hole is still blocked by the rebar. Then you have to cut the rebar in some fashion to get in.

As soon as I read about square roots, I decided to house rule this nonsense. I thought I left this kind of math behind in SR3, nyuh. Anyone have an simplified houserules for this stuff? OR, we could come up with a chart? I dunno, but my runs are fast paced enough that if my runners are stopping to calculate square roots and stuff, they'll most likely get cacked... and I'd like to see an "action-movie" sequence every once in a while where they can just plant an explosive and have it go off. But you know, that's just how I roll.

Yes a table for explosives would be a nice idea but could be a lot of work think about the variables.

Well, first off, if the runners are in a hurry, I seriously doubt they would stop to make a calculation on how many kilos they need, exactly, to breach a wall/door/whatever. The smart ones will have this all figured out ahead of time, and will have the chart pulled up on their commlink/image link. Either that, or they bring along more than enough explosives to make their exit, and just don't worry about the exact quantity needed to do the job. The only time I can see a runner sitting down with a calculator and doing the math is when time isn't a factor, and this can happen quite often.

As for a quick chart, Arsenal has just that...but I'm not sure if posting it would be against copyright laws or not. Honestly, if you have some time, a calculator, and index cards, you can make your own chart and just have it handy for when you are playing.

Personally, I've created a spreadsheet in excel that does all the calculations for me.

Edit: Square roots aren't terribly hard to figure out, especially if you have a calculator. Look earlier in this thread...the formulas are realtively simple.

Mind sharing that excel sheet with the rest of us

Sure. Gimme a place to host it and I'll put it up for all to see/use.

I too used a spreadsheet for use with the old "Demolitions" skill, all I have to do input the armor value, value of the explosive, and numbers of successes, then it gave me the amount of explosives to put a 1 meter hole, 2 meter hole and to totally destroy the barrier.

But since the Arsenal rules have come into light, I have not yet modified the sheet.

WMS

One of the marks of someone who knows what they are doing is they don't stop to look stuff up for trivial issues, and know when and how to methodically solve complex issues. A skilled explosives expert will have some rules of thumb that will get stuff done when speed is more important than finesse or cost. If he's doing complex work that requires precise effects or minimal explosives on hand he's probably going to start crunching numbers.

Also guys who have demo 1 and don't spend 10 minutes setting up the charge in a very methodical, checklist fashion tend to not be around long enough to learn demo 2.

Especially when they like to wear wool and play with electric blasting caps.

Some of the variance is between contained and uncontained blasts. If you put a big barrel of ANFO on a concrete slab in an open field the pressure wave will follow the path of least resistance and leave the concrete fairly unscathed. Put the same ANFO in a van under an overhanging building and you've added constraints to the blast that do much more horrible things.

Of course, high energy/short duration events, like explosions, tend to have their own rules. Explosives can be used to weld, bend, cut, and demolish all kinds of things in counter-intuitive fashions.

Getting back on topic, I'd say simplify the mechanics. A lot. My quick'n dirty suggestion would be to reduce the size of the effective hole by the demolition (cutting charge) Test (Threshold 1). E.g. MadBomberWhatBombsAtMidnight (MBWBAM) gets wants a 7 meter diameter hole. He gets four successes on his demo skill. (4 successes -1 threshold = 3 net) MBWBAM now calculates the explosives needed as if he were making a (7-3net successes =4) meter hole. The counter is that it takes ~1 minute/kilo of explosives as you shape/sculpt them into the right configuration.

Okay, lets see how this pans out.

First, let's assume Rating 6 Foam explosive, since that's the max rating you can get at chargen.


BREACHING

We start with a Reinforced Wall (Armor: 8 / Structure: 9)

We use the base rules for breaching, assuming we are able to spray the foam explosive on the wall, 3.5 meters up (if we want a 7 meter diameter hole)

DV required = (Radius[m] x Structure Rating) + (Armor Rating ÷ 4)
Explosive weight = (DV ÷ DV Multiplier ÷ Explosives Rating)squared in kg


DV required = (3.5 x 9) + (8 / 4)
DV required = 31.5 + 2
DV required = 34 (rounded up from 33.5)

Explosive weight = (34 ÷ 2 ÷ 6) squared in kilos
Explosive weight = (2.83) squared in kilos
Explosive weight = 8.027 kilos

So if we are simply breaching, we can get that 7m diameter hole with 8 kilos of rating 6 foam explosive.


Cutting the same hole should take a much smaller quantity of explosives, so lets see how your suggested rule works:


CUTTING

Assume we make 4 net hits on our Demolitions (Threshold 1) test. That gives us 3 net hits (just like your example)

Just like your example, he uses the breaching rules, but assumes a 4m diameter hole instead of a 7m diameter hole.

I'm also going to assume we use the same x2 multiplier that we did for the breaching calculation

DV required = (Radius[m] x Structure Rating) + (Armor Rating ÷ 4)
Explosive weight = (DV ÷ DV Multiplier ÷ Explosives Rating)squared in kg

DV required = (2 x 9) + (8 ÷ 4)
DV required = (18) + (2)
DV required = 20

Explosive weight = (20 ÷ 2 ÷ 6) squared in kilos
Explosive weight = (1.6666) squared in kilos
Explosive weight = 2.7777 kilos


Not bad. As long as we use the same multiplier, cutting almost 3 times as efficient as breaching.

However, that ratio changes A LOT if your breaching charge is above the ground AND tamped (only 3.56kilos needed).

And Breaching actually gets BETTER than Cutting if you can put your explosives inside the wall, or underwater and deeper than the radius of the hole (2 kilos needed).

And how would you handle something like the linear cutting charges in Arsenal? Or what if you need a square hole cut instead of a round one?