I've not seen a thread on here that has ideas on how to post metal safer. so i thought i would start one. Start with the basics. don't use your home address. even if you don't store your metal at home it could possibly make you a target. a P.O box is the way to go. PM's are quite heavy (might spark the curiosity of an unscrupulous mail sorter/postman) when i pack up something to post out, i try to put as much "filler" scrunched up news paper taped into balls and put them all around the outside of the goods. some post offices sell little inflated airbags also. the extra size hides the condensed weight. even in a satchel. It's always best if nobody knows what you are posting. Always get tracking. if for no other reason than peace of mind. it can be stressful having things in transit. I'm sure other people have suggestions or things to add. I'm not posting this cos of any negative experience i have had, just thought it might be a useful thing to have.
Label it as a engine part, or something else that won't draw attention from postal workers. Also boxes draw less attention than heavy plastic express bags.
Package it tight and securely .... clanging metal inside an express post bag is reprehensible, so don't be a tight-ass with packing, and if you don't have the packing ready, then don't list until you are sorted. Disguise the bulk density, and put thought into the centre of gravity of the parcel .... concealment is the key.
Extra packing for sure, try to beef up the size to compensate for high density metal/items. Having two kilo bars in in small post-pac sliding around in a 3kg satchel will look a bit obvious.
All the above suggestions are good. The bare minimum should be tracking but I'd suggest (if your carrier offers it) for valuable parcels, signature required and even insurance. Also, I save virtually all packing materials I get from orders of any and everything I receive....to be re-used. Saves money, time, and better for our planet. I now have enough styrofoam and corn/wheat-based packing popcorn to last a while. .
...wrap the outside of that package every which way with packing tape. Helps prevent accidental & not-so-accidental mishaps..
Signature is a good idea, but with Aust Post anyone can sign.. So it kind of only negates the point. I often just put a little squiggle because those electronic things they have are damn near impossible to use I was under the impression PM's aren't covered by insurance. With Australia Post anyway??
If you can video tape the wrapping of the product from beginning to end including the labelling and your initials on the parcel proper. I do this for ebay myself to ensure that a) goods can be seen to go into the bag and b) that the address is correct and c) that this marries up with the con note number.