How long is a piece of string???
This is a tough question overall. In my experience every firearm has its favourite recipe, whether factory or handloads. The amount of variables are boggling, from rate of twist in the rifling, to barrel lengths, temperatures, bullet weights, powders, primers, etc etc etc...
I found as I am sure many others have, that in keeping everything the same and just changing from one manufacturer to the other there can be a vast array of differences.
Even a rifle made by the same manufacturer may have a particular type that works great in mine and not in your very same rifle.
With regard to "surplus" ammo, we need to accept the fact that what is really deemed "surplus" in todays world are mil-spec calibers. Typically, military rifles are built to serve a purpose and not require sub MOA accuracy.
I know that some may jump in here and defend a particular rifle, caliber or design and thats fine but as a generality, a 2 or 3 inch group at 100yds will do just fine, considering the technology of the day, iron sights etc.