How to copy weight paint to other arms

Question

So I'm attempting to weight paint a model that has six arms floating away from the main body. My issue is that I satisfactorily weight painted one of the arms, but now I want to copy that arm with its weights to all of the other arms. Unfortunately, the weights don't seem to be copying correctly, and I'm unfamiliar with how to go about transferring them. Does anyone have some tips on how to go about doing this?

I've copied all of the arm meshes, so they should be exact duplicates, and I've copied all of the skeleton bits for the arms, so they should also be exact duplicates, it's just a matter of transferring weights from one arm to another.

In this image, the selected arm is the one I weight painted:

Trying to attach the Blend file through BlendExchange, but it's giving me an error, will keep trying if the file is necessary.

Answer 1

A bone moves vertices that have a vertex group weight that matches the bone name.

Starting with the weight painted arm, in edit mode select the arm and use P->separate by selection. In object mode, duplicate the new arm object and move it into position for another arm. Rename the vertex groups in the duplciate arm to match the corresponding arm bones, eg. rename arm1_upper to arm2_upper. Repeat for each arm.

In the original mesh, delete the arm meshes. In object mode, select all the arms and then the body, use ⎈ CtrlJ to join them into one mesh. Each arm bone should now move the matching arm.