Actually I had two Commander 4.25" barrels also. The difference was 50-75 fps or about 8%.
Do you see a theme emerging here? If we have a 7% difference from high to lowand add another point for the 3/4" of barrel. For practical purposes it don't mean doodly. Do not get fixated on numbers or small differences because there are so many possible variations among guns and ammo that ,unless the sample is really big ,we can't say a difference- let's say 10% for the hell of it- may be nothing more than random wandering of numbers.
For example the two Commanders averaged 766 and 812 with ammo from the same box. Which one is RIGHT???