You can. I had trouble with it too, but I laid it on the ground and took the ammo out of it and it worked.

So... you can do it, but I dont know why it needs to be empty to use a saw on it.

Hello vendetta and thank you for the report.
We have tested this thoroughly but unfortunately we were unable to reproduce the issue you have described. Keep in mind that to saw off the weapon you are required to empty it first.
Regards,
Geez