My Pre-64 experience... I have a m70 that was originally a .300 H&H, which was rechambered to .300 Weatherby by Roy Weatherby himself in 1955... Some years later the barrel was cut down to 20", the justification being it would be handier for hunting elk in timber
... While it might have made the rifle handier it sure doesn't take advantage of 85 grains of Norma MRP in that big weatherby case... As a result the velocity is a joke, although it makes an epic fireball and the noise is incredible... With Weatherby Factory Ammo loaded with a 180 grain Hornady Spire point it groups right at 1.25" at 100 yards... So its accurate but its barely getting to .300 H&H velocities... My weatherby Mark V will get upwards of 3200 FPS with the same load.. The model 70 is right around 2900...
A 26" barrel is in the works as is a McMillan stock... The factory barrel is a lost cause due to its length and the stock is a tragic as its cut too short and beat to death... I will say that I have no other rifle that feeds a belted cartridge as slick as this 60 year old Winchester...