When Burrard spoke of velocity he was generally using the standard "Observed Velocity" which was the average over 20 yds. The standard load of his day of 3 drams & 1 1/16oz shot had an observed velocity of 1050 fps. Converted to MV it was about 1300 fps. That 1150 velocity would have been over 1400 fps & likely pushing that 1450 fps. This was normally stated for #6 shot. If different sizes of shot were given the same MV, they would have different OV, larger shot being higher than smaller shot.
I think 2 Piper is correct here. Reading some of Burrard's writing takes a little time to digest & Burrard doesn't state the method of obtaining the 1150 velocity limit but taking the entire chapter into context "observed velocity" looks to be correct & Table XII (1150 fps observed velocity) does list #5 shot muzzle velocity @ 1450 fps & #6 @ 1475
Still, that makes the current loads in discussion that are listed @ 1450 fps by CIP methods (measured @ 2.5 meters) likely 1500 fps or more @ the muzzle.
I'm finding it difficult to determine what is normal or standard velocity is when comparing loads using multiple methods of stating velocity but I always considered 12 ga. game loads 1 1/16 to 1 1/4 of around 1250 fps (+ or - 50fps) using SAMMI or CIP velocity standards of measurement as standard velocity loads.
BTW, using Burrard's data & #5 shot the downrange velocity difference @ 50 yds between loads starting @ 1251 fps & 1450 fps (muzzle velocity) is 27 fps or a 4.8% advantage for the faster load & assuming a 6 3/4 lb. gun the recoil increase is 5.5 ft lbs. or 34.5%
