Brittany Man, those old pigeon loads were indeed 1220 fps. I used to be able to get them in 6 shot from Winchester, but they eventually dropped anything larger than 7 1/2. These days, outside of the RST's, try to find ANY quality 1 1/8 oz or 1 1/4 oz load from a US manufacturer at a velocity under 1300 fps.
Re observed velocity vs velocity as we measure it: I have a little note in my Eley Shooters Diary, which records all sort of interesting information about shotshells: comparative US/British/other European shot sizes, etc. I didn't record the source of the note I made, but here's what I wrote:
Standard British game loads, observed velocity 1070 fps = American velocity 1175 fps. High velocity observed 1120 fps =American 1235 fps. So looks like adding about 100 to an observed velocity figure is going to get us to our 3 foot velocity. Add another 100 fps or so to that and you have the true muzzle velocity.
