Biggest is a 16.5lb 4 bore, 383gns 2F, 88gns lube and wads, and 2133gn conical at 1200fps. Knocked my glasses off and almost dropped the gun. Decided to back down a bit!

But the Worst..
Yet another Marlin, a 16.5" unported 50AK (an even 3kg) with a 13" lop. Shot 10 rds of 525/1865 before deciding this wasn't fun anymore and haven't touched those loads since.

Bob