Okay I made a working proof of concept on this, but right now the sprites are shitty , and the gibs are wrong, as well as the one of the sounds. (I put thud noises in but a metal sound is hiding in the wound code somewhere)
There are other problems with it too but this could really work.

I plan to make two main types, pinned and unpinned, as well as a few pre-built walls and bunkers using them.

If anyone would like to lend a hand, your help is much appreciated. (sprites are needed most right now)

-and yes the sprites are awful.

I'm pretty sure someone already made something LIKE this.

Hmmm I will search, because its something I think would be a great addition to the game.

(note: I have not tested this yet)
This sounds like it would actually be pretty cool. I can sort of picture a pile of unpinned sandbag objects,
that would all fly back if you shot a rocket at them. Something like that. I'll dl and see what it really does.

That's what I was imagining Problem is I just tried unpinning it and the bags stack just the way I wanted them to, BUT they become terrain from the crush damage of them selves.
Also the AI seems to have problems seeing them, they try to walk through the as if they are not there at all.

So sadly if I stack the unpinned sacks, you may as well be hiding behind grass.
but I could fix this by stacking one or two on top of a pinned crate, or making pinned stacks and walls of sacks.

pin it into a pre-made bunker piece or something. Maybe just a floor but with them pinned. And don't pin them too hard, so that when a rocket blew them up you can see some sandbag flying about.

If you give them a PinStrength of 1, they won't settle until they've been shot, but it will be just enough that the lightest touch will send them flying.

Okay I will test that when I get home thanks.
(starting a new job )

Yeah, now that I tested it... It bleeds sand!!
And I was thinking more like the above, or maybe something like Deathbringer's obelisk. Sort of.

I will do some tweaking today on the sandbag project. As mentioned by a few of you I will lower the pin strength by a lot. I will work on getting the sand to come out and pile up rather than disappear, and make a few sand puffs in the gibs.

Contrary may help with the sprites, but that's going to be a week or two.

If everything works out, we should have bags flying off from rocket explosions in no time.
(If you want feel free to make changes of your own and post it here)

*edit*
Okay pin strength works, but certain types of damage make them terrain instantly.
Now the bags explode into puffs of sand, and bits of bag when they gib, and they no longer sound like metal.
I'm going to have to play with the gibimpulselimit, I think the wounds should stay high due to sand bags can take a lot of bullets. (I use them when I shoot at the local range)

No idea what that is

That would be this lovely destructible here http://forums.datarealms.com/viewtopic.php?f=61&t=16805&start=0 no idea if it will help but you might be able to pull some ideas from it.

On another more topic inclined note I think that having sandbags to shoot around is a great idea and I can't wait to see the end result.

I took a look at the deathbringer's obelisk, and that's close to what I'm doing with the gibs.
I already made cloth gibs, sand puffs, and plan on using maybe some smoke as a quick dust effect. If you look at the new version you can see I'm heading that way.

Ahh sorry sorry. >.< I've been busy...

I'll start RIGHT NOW. Could you give me a kind of explanation of what you're going for?

No problem
After messing with the code a bit, I think just a few variations of the same bag that stack nice would be perfect. Ooh and my comment about a week or two was just the time scale you gave me not sarcasm, some times its hard to tell the difference in writing.

I almost have the bags flying around perfectly after a good rocket hit.
I will post a new version here in a few.

*edit*
One minor problem before I post a new version, the sand doesn't pile up from the bleeds. Does anyone know how I can fix that? Is it a friction issue with my material?

*fixed more things*
It was stickiness, now the sand piles right.

Also recolored the sand to match better
added dust cloud effect
reduced gib limit
reduced mass so pieces will fly more.

Got a sneak preview of the new sprites by Contrary, they look great. (not included yet)

*update 2-20-10*

Rather than bumping my own topic, I thought I would update here till someone posts a reply.
Right now I'm working on making a few varieties of bags, with different properties.

I have found that if my pin strength is too low, the bags become terrain easily. (even flying over with a jetpack can cause this) So I'm looking at a few solutions, and working on making bags that are good for different things.
I hope to have a new version up soon.

Sorry to necro my own topic, but I have been working on fixing a few more things on this.
I changed the sand bags from being a MOSRotating to a ADoor, now the enemies can see the bags and properly attack them.
I also added a bit of lua to remove them from the kill counter, and have been tweaking the wounds to reduce lag.

I have yet to switch out the bitmaps with png's but I will do that soon.

All and all I think I have solved the issues that have been preventing me from releasing this mod.