What I meant gewehr76 is that the guns are always proofed higher and can therefore handle more pressure than standard loadings but proofing over an over again is bad, the No 4 Enfield can technically take more pressure than the older generation enfields so the ammo is loaded down for the older versions, I assume that is still the case with the 7.62x54R.
What I was leaning towards though is the evolution of the military surplus ammo and how pulling a bullet and seating another is not something to just throw around. If you have flat base military 180gr and you pull the bullet and seat a flat base 180gr SP to the same seating depth into the powder then you should not have any problems at all but there are a number of factors to take into account. First off there have been many different bullet weights loaded over the 100+ years of surplus, if you have 150gr military ammo and you seat a 180gr SP you have the potential to be over powder by approximately 10% based on the numbers for H4895 from IMR, so verify the bullet weight first, I know that surplus packages are not well marked for this. Another thing to consider is the base, a flat base vs a boat tail will have different pressures, the flat base generally has more contact to the bore on firing but a boat tail creates little pressure spikes around the bullet, they will not act the same way, hence why I said building a load (starting by losing 10% of the powder and trickling up) is a good idea. Another thing to consider is the way the bullet is made, the steel bullets are very long for the weight, a .311 125gr is about the same length as a 150gr .311. Pulling a steel one and seating a lead one at the same OAL should be less pressure as it will not be seated into the powder as far but yet seating say a Barnes into a military case to the same OAL as a lead core FMJ bullet would seat it deeper and potentially cause pressure issues.
You are reloading when you do any of these things, learning the load and how it reacts to your gun is what is needed, blanket statements are hard as there are lots of variables. If I were wanting to hunt with a Mosin I would probably go boxer primed brass though, no corrosive primers to deal with when hunting, sure when coming back from the range you plan for the proper cleaning but in the cold of a camp situation with maybe a few friends over I would hate to rot out a barrel by being too busy to properly take care of the rifle.