Copper bullets were more likely to weld and sooner than gilded metal bullets in my experience. Even some bullets like Swift A-Frames and Kodiak that are gilded but seem to have a higher percentage of copper were more prone to weld. Ammo that has been in airplanes also was more prone. I guess they got de-pressured and then when they normalized pressure they took in some humidity. Motor mica definitely helped to reduce the cold welding or corrosion. Same for Hornaday One Shot lube.

I am definitely going to check my older rounds.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli