As pointed out above, there are two considerations to keep in mind vis-a-vis barrel length. One is cartridge performance, the other handling. I use only 22" barrels on my bolt rifles for DG (.505, .500, .450 Watts, .375 H&H). By the same token, all my DRs have 25" barrels (.500 NE, .458 Winchester Mag, .450 C&W, .375 H&H, 9.3X74R, 8X75RS), which results in virtually the same over all length for all rifles.

Cartridge performance with regard to barrel length is a function of expansion ratio. A virtually straight sided case like the .458 has a very high expansion ratio: that is, when the bullet travels the length of the case down the barrel, the volume of expanding gas virtually doubles. In a sharply bottle necked case, this is not so, and the bullet from a 7mm Remington Magnum, for instance, has to travel much further for the gas volume to expand the same amount. Some cartridges, like the .22 lr, actually lose velocity beyond a certain barrel length. A .22 lr cartridge shot from a 16" barrel will have higher velocity than one shot from a barrel either shorter or longer than 16".

What this means in practical terms is simply that reducing the barrel length of a rifle using a cartridge with a high expansion ratio, such as most DG cartridges, has minimal effect on velocity, so that handling qualities far outweigh cartridge performance as a factor in determining barrel length.

Stated another way, cutting three inches off a 28 inch .458 barrel might result in a 75 fps. velocity loss, while reducing a 7mm Remington Magnum barrel the same amount might cost 300 fps. in velocity.