Odd... does for me on the z axis in Sauer - by selecting it, pressing the R key and scrolling the mouse wheel. I don't think you can set the rotation when placing it with "newent barrel 90" as it will read the direction as the mapmodel number.

playerstart, teledestination and mapmodels all take their original orientation from the direction you're looking at when the command is issued;
as steve_e says : R + MW will rotate it to your aesthetic requirements ... or use the "entset" command, shortcut bound to the DOT-key on your numeric keypad :)

I use R and mouse wheel, but it won't rotate it. It works for all other mapmodels though... May be I'm not doing it right? I made a .cfg file and put in those two lines you mentioned in readme. Then I go /sp mapname and edit it from there. For barrel, I just type /newent barrel and your TNT box appears automatically.

I have found it can be difficult to select barrels - can you see the arrow head when the mouse is over the barrel?

With a mapmodel you tend to be able to have the model stuck in the ground as such to align it with the surface, but with a barrel the registration of the xyz (particularly z) axis is critical otherwise the barrel will not sit on the surface but float either ontop or below the surface. So, what this means is that the barrel selection is often stuck inside the barrel and trying to select them can be problematic at times.

As I said, I have had no problems rotating this mapmodel (or about 5 others I have created of late) - but, yes, at times they can be a pain to select.

Apart from that I would have no idea what the problem could be as it is just a .md3 like the other .md3 models and there is nothing in the file as such that limits the rotation of the object.

I was able to rotate it finally :). I found that it rotates not like the other mapmodels. First, I have to rotate it, then press E to go into normal mode and press E again. After that it'll show up in the right position. The same problem with moving them (and all of the barrels): you're moving the box, not the actual model, and after you press E twice it'll appear in a new position.

Oh yeah, you have to press the edittoggle twice to update the positioning of boxes and barrels - they behave differently to mapmodels. Glad you got it sussed out. Cheers.

It's because the barrels and boxes (boxen?) are actually AI things, like the monsters. The platforms and elevators are also the same, though I'm not sure if they are implemented the same way.

Oh, and the node name says this is a barrel, but it's a box. Huh? I understand it's a box for use as a barrel, but still...

Yeah, it is a barrel in the shape of a box... well, I didn't want to call it a box as it was designed to be a 'barrel' - ie, to explode, rather than its shape as such.

My current task is exploring the art side of the mapping (textures and models) so I will/have been producing a few little models and doors. I have produced a door and a gate, so I might post them up once I have refined the UV mapping. Cheers.