The pull tab isn't 'welded'-it's just soldered. Trust me-I've bought this same ammo before.
Grab a pair of gloves and some eye protection. Then pry up the pull tab a little with a knife blade and slip your middle finger through the tab. Now all you need to do is yank that sucker with all your might and it'll bust through the solder and you'll have a nice open can of 300 rounds.
So all you need to do is pull on the thing. No need for chisels, hammers, or Dremels. Just pull.
Occam's Razor, as they say.