Back around 2003 or so when we made a few test guns for the Coast Guard for what became the 82A1CQ, the Coast Guard asked about making a few 50rd and 100rd drum mags.
Ronnie said "Not going to entertain the idea"
A drum that large would need to be electrically driven.
A few of us took 2 10rd mags. Cut the top 3/4" -7/8" off of the top of one mag. Cut off the bottom floor plate tabs on another mag and TIG welded the 2 mags together to make what we called "Super Mag"
We stretched the hell out of the mag spring to help lift the rounds.
1st one worked great. So we made another one. That worked also.
We used those 2 mags every now and again at the range for shits and giggles. Ronnie saw one of them laying out on a work table in assembly and asked us to keep them out of sight or someone may see it and start asking to have them made.
Wish I had taken a pic of it back then.