Well, I'm not sure exactly which 3do editor you used. If you did something in a weird order, it wouldn't have been hard to screw up the node hierarchy of the 3do.
I'd suggest trying to do this with a text editor. Find the rail detonator model mesh, and copy&paste a concussion rifle mesh section directly over it. Add the MAT references at the top of the file and change the corresponding numbers in your newly pasted concussion rifle mesh and it's all done. If you wanted to rotate the mesh or something, then a 3do editor'd be good for that.
QM
I'd suggest trying to do this with a text editor. Find the rail detonator model mesh, and copy&paste a concussion rifle mesh section directly over it. Add the MAT references at the top of the file and change the corresponding numbers in your newly pasted concussion rifle mesh and it's all done. If you wanted to rotate the mesh or something, then a 3do editor'd be good for that.
QM