Is there a variation of the Bowline that can be used in demo?

While I was on the final FTX for AIT we set up some charges which were then tied into a line main. One of my drill sergeants tied a couple charges in with a knot that looked for all the world like a bowline. I'm fairly certain he told me that's what it was, but wouldn't explain any further. I know it was not a gregory or sapper knot, or any of the "book" tie ins. Does anyone know of a variation of the bowline that could be used to tie to a main? I don't see how the bowline would reliably tighten up to initiate the det cord.