Thinking about it in those terms will get you really funny results, because of the unreasonably high variance of Blast ratings and Power/kgs of SR explosives. With just Commercial Explosives, though, it kind of works out, because the actual blast radii of all types are equal.

I seem to remember from my explosives training that a series of 0.25kg TNT charges will only go off if the explosives are within ~20cm of each other. That'd make it ~40cm for a 1kg TNT charge. As a quick rule of thumb, then, you might use (explosive charge weight)^0.5 x (0.5 meters); 1kg = 0.5m, 4kg = 1m, ~15kg = 2m, ~60kg = 3m, etc.

A Hand or Minigrenade would probably have to go off in contact with or right next to the explosive to detonate it.

If you had C4 detonate right next to but not touching another lump of C4, the second wouldn't detonate. Without the current it would just get blasted apart and not blow up it's self.

Unless it was shoddy C4 wannabe stuff. In that case it's up to the GM. The higher the quality, the close it can be to the point where it's just incinerated without explosion.

When I was overseas, I had to treat a dude who blew his leg off doing this.

His buddies said he was using a piece of lit C4 on a stick to heat some food from a field ration and when he finished he threw the thing on the ground and stomped on it to put out the flame.
<BOOM>

There is plastique that will ignite from just an electrical current but really, nobody really wants to risk using something that unstable. Well, maybe there are some that would, but nobody I know at least.

Well, it really does depend on the explosive in question, as KaOs said, and a bunch of other factors. I personally haven't got any experience with C-4, just a few other explosives like TNT, RDX, and some others the exact type of which I'm not sure, but most of those can certainly be set off by another major explosion happening very close.

On the other hand, I did witness some type of plastic explosive where some moron had rammed the blasting cap through the charge itself, the result of which was that the 300g block of explosive had a 5cm/2" diameter hole through the middle but had not detonated. You can believe we nearly shit outselves when we noticed that lying on a smoking tree stump in the training area.

i think the exact statements is that you can get compounds that detonate on anything from a simple battery spark to something that needs more brute force to have it detonate. the stuff in the books are not so much diffrent brands and blends but diffrent detonation classes, you dont want to bring out the C12 if all you need is the comersial stuff, control is the most important thing in demolitions. if you dont have a general idea of how far stuff will fly then you may well be useing to much...

still, this have no real effect in SR rules as the damage rating dont take shrapnel into account, if so then the power reduction pr meter may have been much lower...

whatever you do, dont compare grenades and other explosives in SR. they work under diffrent laws of physics

This makes me laugh. If it was C4 there is no way that happened. Unless it was homemade. Military grade C4 is stable unless it came from a really really bad batch. Hell, I doubt that would explode either.

The Blast ratings of commercial explosives don't take sense into account. They are, how can I put this gently, fucking bullshit.

Yep. Very stable unless exposed to, you know, both heat and pressure. The current is irrelevant to the C4, so your other statement is entirely wrong as well.

~J

What do you suppose would happen if I were inside there? I mean, I'm not that big. I could fit in there OK probably.

Kagetenshi's numbers look about right. The explosion in the detcord certainly doesn't travel faster than electricity in a wire -- it is orders of magnitude slower. The blasting caps may indeed provide an answer here. Perhaps (some types of) electric blasting caps ignite slowly, ie. take a noticeable fraction of a second to detonate after the current runs through them.

Did the

under Commercial Explosives get errata?

I remembered it as you say, but looked it up when I started the topic.