Why are people buying up the birdshot?

[FrommerStop]

They finally blew up the gun using 45 grains of range trash and a 405 cast bullet loaded into a .454 casull case.

Gun after it let go. The choke was still 0.387

Above from their video of 'What Happened to "9 Lives" '
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[MarkS]

I've made wax shells by opening 12 gauge 7 1/2 birdshot shells then pouring the shot out. then putting in a little birdshot and dripping wax on top of it then adding more birdshot and wax in layers until full, Once full I closed the shell up I did a few more 5 or 6 that I used to destroy an old nonworking desktop computer. I didn't take pictures but they made a hole like a slug would have on the outside but splattered on the inside just like in the videos I got the idea from.
Shot them out of my singleshot 12 gauge with a 28 modified barrel