A case for the Un-Bob
You mentioned a .257 Roberts. After WWII a bunch of vets were really into wildcatting they did just about everything that could be done to a center fire rifle cartridge. Expanded them up, necked them down, messed with the case geometry. The 7x57 was a child of the Mauser family. Americans messed with the case but the shooting culture was very prejudiced against things German. In necking the 7x57 down to .257 they got a light, accurate round with good speed (at the time 30-06 was the gold standard with 2700 fps and a little heavier bullet). They renamed it the .257 Roberts to ward off prejudice against things German (Wildcats were traditionally named after their inventor).
I guy named PO Ackley perfected a way to improve performance through improved chamber geometry. He applied it to the .257 and obtained good results. The thing with the .25s is that they are all overbore (it might be underbore), meaning that the reduced bore size restricts the amount of powder you can burn because of chamber pressure and short barrel/throat life. 25/06s show max loads at or about 50 grains. Some people do load up to 55 grains but they pay a price and they know it. Blown primers, short case life and shorter barrel life.
The .257 Roberts hits peak performance at or about maximum pressure levels. They are inherently accurate and they push a 120 grain bullet to 3100 fps with a 24 inch barrel and they are very low recoil compared to the competition. I have heard it said that the .257 was PO Ackley's favorite round.
In 2000 one of the big gun magazines picked the bolt action of the century and the Mauser 98 was # 1. With 50 grains of H 4831 SC and a 120 gr bullet, sighted in for 250 yards (2" high at 100 yards) you have point blank shooting to 300 yards.
The three cartridges shown are left to right are a .308, a .257 Roberts Ackley improved, and a .270 (I don't own a 25/06 and they are very similar to a .270).
The result is a rifleman's rifle, a snapshot of one man's example of striving to attain perfection (I did not build this rifle - I just shoot it and polish it).
Higene