Back in the 1960s and 1970s 98s were dirt cheap and many of us cut them down, cut them up, modified them in all manner to end up with a rifle not as good as a factory Remington or Winchester.
Now unmodified 98s are worth too much to butcher.
Yes, start with one already modified. Value is gone. But you wtill wind up with a rifle that's not as good as a decent factory offering unless you go full bore custom by good smith. Do it yourself as a novice rifle maker and you wind up with nothing to brag about.
If the objective is doing the work then buy a cut up 98 and go to town. If the goal is nice rifle then buy one made the way you want it.
Another option might be a commercial 98. Since the 1950s many companies made or imported commercial grade 98s that are much more refined than the old military Mauser. Make much better sporting rifles.
This started at a commercial CZ action with dual triggers. I stocked it in walnut in classic European style including steel butt plate, barrel mounted front swivel, and hooded front sight. It came drilled and tapped but I opted for a receiver sight rather than a scope. Added a 30-06 barrel from McMillan and the finished product is a quality sporting Mauser that was faster, easier and cheaper than starting with a military model and collectors aren't screaming for my head.
Compare the above rifle to this one I did a few years ago. It started as a Colombian Model 98 that was in terrible shape so no collector would howl. Stocked, updated, refinished, it just doesn't look as refined as the CZ pictured above.
Now this 1924 Mexican Mauser was also in horrible shape when I got it. In fact, it was just an action. No wood or barrel. Gave it to a good smith and he made this. But it wasn't cheap and it still isn't as sophisticated looking as the commercial model.
So again, if what you want is nice rifle when you're done, I suggest starting with a commercial gun. If what you want is the experience of reworking the rifle, then find a beater and have at it.
By the way, this is what a European smith did with a military 98 back in the late 1940s and 1950s.
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