The cost of a 257 Roberts by Browning will depend on the condition of the rifle. Prices range from $850 to $1,175.00.
When the bar was first made in 1967,the rifles were not made in 257 Roberts.They were made in 243 Winchester,because of the popularity of that cartridge which made the 257 Roberts pretty much overlooked.
Browning only lists two action lengths for the BLR, standard and long. The 257 Roberts is in the standard action. It can legitimately be used in a short or long action depending on the bullet used and the maker of the rifle.
Value of 257 Roberts Model 722 Serial No/ 319811
Quite a few different ones. Some of the more notorious ones were war souvenir Japanese Arisaka rifles, which had been converted to fire the .257 Roberts, as the Japanese ammunition was a bit scarce on the commercial market. I know the Ruger rifles were made available in .257 Roberts, including the Mk. II and M77, as were the Winchester Model 70, Browning Model 81, and Remington 700. Sako made custom rifles in that calibre, as well.
Value is too difficult to be accurate without seeing the gun. Recommend taking it to a gun shop for appraisal.
The short answer is no. Although the two calibers have the same parent case, 7mm Mauser, the 257 uses a .257" diameter bullet and the 6.5 Roberts uses a .264" diameter bullet. They are not interchangeable.
Based on an exhaustive Google search, I don't believe so. They did make a .257 Roberts, at least in 1942, and it is rare. Sometimes these were reamed out later by gunsmiths to .257 Weatherby Magnum, and the barrel markings may or may not have been changed.
1951
Short
Is in excellent condition.
100-400 USD