A good friend (now deceased) and myself spent close-on 25 years tinkering with old military rifles. He was interested in rifles used in the Boer War and the two World Wars. To this end, we tested German, British, American, Japanese, Swedish (they were available), Norwegian, Russian and Canadian rifles (Rosses and Lee-Enfields both). Through this all, we came to a few conclusions, guidelines, whatever you might call them.
For best accuracy, we found, you can handload almost any of the military rounds to 10% LESS than Service velocity. This SHOULD result in SAFE, LOWER pressure levels.
Seating should be just off the lands.
Wartime tolerances led to some amazing variations in bore and groove diameters. You can compensate for MUCH of this variation by using FLATbase bullets.
Military ammunition tended to use FASTER powders, as this meant less tonnage in transport and for the PBI to have to cart around. YOUR RIFLE MAY WELL DISAGREE.
Many military rifles were stocked with tight action-to-chamber bedding, floating barrels and a 1- to 2-inch damping point at the front end of the wood. If you are bedding one yourself, this is a good starting-point. Here, the ONLY exception is the SMLE, which has a midpoint bedding rest.
Enfield rifling -- 5 deep grooves, left-hand -- DEMANDS flat-base bullets. The later Enfield 2-groove rifling also performs well with flatbase bullets with softer jackets.
OTHER rifles which may demand flat-base bullets with softer jackets include Carcanos and the Type 38 Arisaka.
The Rifle is the Boss!
Screws tight.... and the ONLY exception here is the Magpie Screw on the SMLE.
Follow these rules religiously and you will find that the majority of military rifles which have not been abused can turn in accuracy approximating 1-MOA if you do your end of the job.
Good luck!