I measured a 16 gauge Brenneke slug shell, and the OAL was 2 1/4", with a rolled crimp, so I believe they can be used in a 2 1/2" chamber with impunity.

My main concern is with the choke, which with the right barrel of my Greifelt drilling is so tight that the measuring device could not be inserted in the barrel. The left barrel measured "full choke", so I refer to the chokes as "full and fuller."

I have been told that Brennekes will shoot safely in even the tightest choked barrels, but I'm just not sure how accurate that representation is and how much I trust it.