In the 14 bore (.69") - at 200gr. 2F - in the late 80's using GOEX, I recorded 1,700fps. While doing this chronographing at the jail range, I accidentally dumped in a double charge of my 'hunting' load of 165gr. (1,550fps), which of course was 330gr. with a single ball and that one, also over the screens, gave me a whopping 1,770fps, but did lift me off the chair and taught me to be more careful - that one hurt a bit.
That was the same day, using a single patch and 3 drams of 3F GOEX (1,225fps), I shot a 5 shot group at 50yards measuring 1 1/8", the patch collected after each shot, then spit on it to relube it for every shot of the group. The group was shot sitting at a table using sand bags as a rest, without wiping between shots.