I've personnally done better (more boneheaded)than that:

With very little time to pack... I grabbed a 54 instead of a 50 caliber rifle.

Went hunting on a remote pack-in hunt and brought 54 caliber rifle instead of the 50 caliber I was planning on taking. My hunting pouch and loading block was all set for 50 cal. All my patches and roundball were .490". The other twofriends I went with had plenty of 50 caliber ball as that's what they had for rifles.

Needless to say, I even went so far as to usefourpatches around a 50 cal ball in my 54 only to find out it still shot terrible outside of 20 yards.

So, forfive days I loaded with a .490 roundball and my four patches and I waited for a deer to come and sit in my lap so I could shoot him. I was bummed. I still get ribbed from those two guys and that was almost 20 years ago.

Tahquamenon