Ok, I'm by no means an expert. I re-finished a couple of original stocks and I'm in the final bit of finishing one from new.
However, in the process of educating myself I read few good books written by widely acknowledged experts. I suggest you read at least "Gunstock Finishing and Care" by Donald Newell. If you're having trouble finding a copy there is an electronic one floating on the Internet. It has been written in 1949 so it may be out of copyright. Pm me for the link.
Coming back to your question.
I don't know if the military ever used raw linseed oil. I'm not sure why would they choose to do such a thing when it may have been known adding small amounts of certain metal salts makes it dry a lot faster. Also operations such as boiling, storing in sunlight, even simply storing it outside thicken raw oil and consequently make it dry faster.
I don't know who was the first person to invent which metal salts to use as driers, but we know inks used in ancient Rome were based on linseed (and other drying oils). Painters have used it for a very long time. Also painters use various metal salts as colors (lead white, for example). It was probably discovered many times that mixing some of those salts in makes the oil dry much much quicker.
Additionally I read somewhere (so it may be conjecture) some old French muskets were dried for 14-21 days after dipping. I'm not sure this is enough time for raw oil to dry.
Now, let's address the practicality of using raw linseed oil in modern times. There is literally none. I was told it takes a very, very long time for raw linseed oil to dry. It is possible for it to remain tacky for years. While with boiled linseed oil, you only have to wait few days between coats (if you have a warm box, or live in a warm place - in winter it may be a different story). Once boiled linseed oil polymerises(dries) it is exactly the same thing as if raw oil was allowed time to dry. The only difference is minute presence of those metal salts mentioned before.
Personally I would never use, nor recommend raw linseed oil to anyone. This is advice I read repeatedly in many places.
Also, on subject of use of any form of linseed oil. If your desire is to have simple milsurp-type finish. Few coats will do. That's exactly what I did on one of my plain original guns.
However, if you want to achieve any kind of "depth" in your finishing be ready for it to take months before you have enough coats of boiled linseed (or years if using raw linseed) to achieve any depth.
Rubbed dull finish can be achieved quite easily with modern varnishes (Gunstock specific ones - some swear by tru-oil, or even generic ones like good quality oil based polyurethane).
Also regarding sealing of inletting and other essential places of a stock regardless of final finish choice, I read about, and I used a method myself where one takes a modern oil based polyurethane, thins it with mineral spirits to consistency of water. Then one applies it as the very first thing (after staining, if one stains the wood) to the whole stock with a brush liberally. The goal being for it to soak into wood. One keeps brushing it on as it soaks in until the wood will not take any more of it. Then the surface is wiped clean with a rag. Once it dries, the wood is sanded lightly where other finishes will be applied later and left as is in inletted areas. Assuming good type of varnish was used (for example a marine spar varnish) the wood shood be sealed from effects of moisture and any other compatible finish can be applied on top.
More coats of modern poly can be applied (with light sanding in between coats) to achieve depth, then one can finish with boiled linseed. Alternatively one can polish modern varnish to look like linseed and be much more elements resistant.
There are other things to consider too, which finish is more applicable, are we restoring an original (I wouldn't use a modern varnish despite its superiority IMO), or is it a modern repro? Will the gun see a lot of use in harsh conditions(modern varnish!). Or will it seat in a safe, or a presentation box and be gently pulled out once a year to admire (boiled linseed?). Etc.
No doubt you'll get many more replies from people using both
I recommend you read the book I mentioned too.