Anyone have a chronograph or know the muzzle velocity of short barrel shotguns at different barrel lengths?

I have been told you only loose aprox. 100fps going from 18in to 11in barrel, I don't have a chrono, I'd like to see what some of these MV's actualy Are.

First, using  birdshot- 12 gauge, 2 3/4 inches, 1 oz shot
12" barrel average FPS- 1040
14" barrel average FPS- 1069
18" barrel average FPS- 1114
19.5" barrel average FPS- 1114
20" barrel average FPS- 1108
28" barrel average FPS- 1159

Then using Remington 00 Buck-
12" barrel average FPS- 1121
14" barrel average FPS- 1127
18" barrel average FPS- 1216
19.5" barrel average FPS- 1205
20" barrel average FPS- 1182
28" barrel average FPS- 1250

Strange nonlinear data points.  Who would have thunk.  Mach 1 on a standard day sea level is 1117.  I guess the real question is "can you run faster than 00 buck traveling at the speed of sound, and if you can't will it hurt?

thanks for the data. I plan on buying a crono so i'll add my 11.5 and 8in data.  I really want to know where the 1600 FPS hornady tap loads are, i have no idea what the test barrel length was on that. I'll bet its still arround 1500FPS

I your remington load is 9 or 12 pellot?

That makes all that extra lenght look silly dosent it?

Looking at these numbers makes a short-barreled shotgun all that more attractive.