What typically causes cold welding?
It came up in a thread awhile back and i did a little experimenting for my own cuiosity.
I pulled some bullets from 1970's production 30-30 win ammo that wasnt in very good condition and some 300Wm ammo i had that had been loaded for years.
Niether had any issues but it was explained to me that one the factory ammo may have had some type of sealent and the reloaded 300wm ammo had carbon in the neck that acted as a lubricant.
I have been lubing the necks on my reloads now for years with no issue (lubing the inside of necks or a turning arbor in expander die) but when i first built my 6.5CM i took a new piece of lapua brass and seated a 147eldm in it for a dummy round.
It seated fairly easy but a couple years later when i pulled it i thought it was going to pull the rim of the case out of the shell holder.
It was a new clean case no carbon or any other lubricant, neck tension was probably excessive as it was new and untouched other than a load chamfer and when it did let go it popped like it had been glued into the neck.