The 6.5s were from a Winchester M-70 with 22" barrel and the 30/30's from the 26" barrel of a Savage 219 single shot which is shorter overall than the 22" Winchester.
Might be reading this wrong, but your saying that the 22" barrel on the 6.5 is only getting 20 something fps more velocity from a 4" shorter barrel? I am guessing here that even with the 24" barrel on the Savage that the complete rifle is still shorter in overall length than the M-70 ? This is generally the case when a single shot is compared in length to a bolt action as the action takes up around 3-4", however it doesn't add to velocity, where as the added length of the single shot barrel does. I guess I am not seeing what the point is, whether your upset at the velocity of the 6.5 from the 22" or the velocity from the 30-30 in a 24"?
Figuring at 50fps per inch of barrel, with equal length barrels being 26", the 6.5 would be roughly pushing 2650fps which is darn close to the original loads for this caliber.
Seeing the original rifles were built with 29" barrels on them, then subtracting the above 50fps per inch for a 22" barrel and using original standard loads of 2650 the velocity would be around 2300fps, so the ammo is still bettering an original load for the barrel length listed.
That said, even with the velocities where they are for factory loaded ammo, it will and does kill all out of proportion from what most people think. But in today's world of ballistics and uber magnums of this that and the other caliber something as mundane as 2600fps will simply bounce off any animal it is pointed at.
Like I said, the 6.5x55 is a great round as is, and will do things way out of proportion to what most think it will, at ranges further than most folks are capable of accurately shooting. Yes it can be loaded up to higher than factory loads "in a modern action", however this is up to the owner and not the responsibility of any of the manufacturers. I highly suspect that if your neighbor came over one day and asked if you could load him up some 45 Colt loads to around 1300fps for his 1898 Colt Single Action Army revolver, you would simply look at him and laugh, but maybe not. Bottom line is society and lawyers, have proven that if it can happen, someone else is to blame, but not the idiot who performed the act of stupidity to begin with. The manufacturers are simply abiding by the standards set, like it or not.