I have to agree with shortmagman....It most likely is not the 2" difference...As a rule you usually get more velocity from a longer barrel...But the difference is not linear...On the other hand...I have a .260 with a 26" Shilen (varmint wt.) and a .260 with a Shaw 24" (sporter)....Both shoot well with similar loads but the shorter one is always just a few fps more under the same conditions and same load lot.....For example my pet load for my .260s is 130 VLDs pushed by IMR4350....The Shaw produces 2914 fps with while the longer Shilen comes in at 2904 with the same load at the same time...15 thou off the lands in the Shilen and .018 in the Shaw....
Any load or powder I throw at them have similar results when the same load is used in both rifles....The Shaw kicks out SDs of around 6 or 7 while the Shilen runs anywhere from 8 to ten based on ten shot strings....The Shilen however usually groups a little better at 100 yards but probably because it is heavier and my poor bag manners show up more with the light barreled Shaw....The Shilen usually shoots in the .3s and .4s in 5 shot groups but the Shaw struggles to stay under .65 but has been down to .25 a few times in three shot runs....
Every rifle barrel seems to have a science of its own....Chambering, bore/land configuration, condition of the bore and a host of contributing factors have a part in what speed and behavior a rifle will shoot.....
Randy