Technically, it’s not an explosion chance which makes the barrels explode but their health going to 0. They have health similar to hedgehogs but you can’t see it directly. You can tell from the smoke how many health is left. The more smoke, the less health.
From what I can tell from the source code, barrels start with 60 health and I think their health increases when they become frozen.

(Edit: But don’t take my word for it, I am not a Hedgewars developer!)

But I understand your point. Configuring the barrel’s starting health would indeed be a nice thing to have.

You're right about the starting health. Freezing a barrel adds an extra 60hp.
Fire is an excellent way to blow up barrels BTW.
Molotov cocktails really do a number on them.

And, yeah, health was deliberately picked so that a direct hit w/ shotgun would not blow them up on starting turn. Thus 60.
Fall damage has been tweaked so you can still bat them and usually get a satisfying explosion.
Firepunch should work too, on a flat surface or to a lower height, although I'd have to recheck it. Might require a slightly lower height.

You can also hammer them down off a girder onto the hogs below, or use a 'nade for it.

A bit of fall damage will put a 'naded barrel which will have like 15hp (or 10hp if you're good at placing), over the edge.

Ah, good to know, thanks! I was just a bit confused that a direct hit with mortar or airstrike didn't seem to do much to a barrel.

As wuzzy stated, a feature to set the starting health to a custom value would be great (or even adjusting sensibility to different types of hits like bullets and grenades etc, like it seems to be with fall damange if I understand that correctly), for then could one create some "barrel mayhem" styles which would require players to be REALLY careful ...

So if that is not a big coding issue, it would be very welcome indeed.

BTW OT (don't know where to drop the bucket of flowers): a big, BIG thanks for the Multiplayer implementation. Seldom had a game where multplayer over the internet had been so easy and smooth to set up. Really great job!

Well... You could just set 200% damage in the scheme and give hogs 200HP to compensate...
As a bonus hogs will get kicked twice as far for extra mayhem.

It seems a rather minor thing to add an option for.
You could make a custom lua if you wanna try it out tho. Is basically a one-liner.
I'll put it on DLC for you if you like.

That'd be great.
It should also be possible to just modify the value of the barrel "health" in the correct file, right? In which (lua?) file is that information stored? It seems I missed the localization instructions of the files, and can't find a matching one in the application package.

Barrel health (as well as the health of basically anything) is hardcoded at creation. Is just that lua can manipulate that after creation.
So...
function onGearAdd(gear)
SetHealth(gear,5)
end

in a lua script would set the barrels to 5hp.
They'll smoke like mad ofc.

Lua scripts sometimes take some random scheme variable and use it as a config param. So, for example:

SetHealth(gear,WaterRise)
Would set the health to the water rise during sudden death.

should be:

function onGearAdd(gear)
if(GetGearType(gear)==gtExplosives)
then
SetHealth(gear,5)
end
end

--If you want to set the barrels to 5 health.

My apologies. Vatten is right. Otherwise every single thing (hogs being the biggest problem) would get 5hp.
I blame lack of sleep

EDIT Oh sorry, your last comments have not been displayed, therefore I had posted this here; kind of bad cacheing on my side it seems. Thanks for the support! /EDIT

---

So, for example:
In resources/data/scripts add barrel.lua with content:

--
function onGearAdd(gear)
if GetGearType(gear) == gtExplosives then
SetHealth(gear,21)
end
--

Hmmmm ...

My Documents/Hedgewars/Data/Scripts/Multiplayer (assuming you are under Windows - ~/.hedgewars/Data/Scripts/Multiplayer for Linux)
or package in a .hwp and put in Data

True, but there’s a downside for using Lua. You can only use one script at a time. You can’t just combine two or more scripts.
Also, you would have to edit the Lua script for each time you want to change the barrel health.
An option in the game schemes would be, on the other hand, much more flexible and easier to use.