Steve? though i cant see the maker on the barrel, id guess that it was rebarreled at sometime, notice that the rifle is parked, and that the barrel is much lighter color then the action, done seperate from the action...
what iv seen over the years, when i parkerize the barrel and action at the same time {together} the barrel turns out darker, as its not a heat treated steel, and the action is a bit lighter, even on 17,s with the ends annealed ..
i could be wrong, but im saying that someone other then out military changed that barrel, likely it cracked during removal of the original barrel, not real sure,...
although....
it may not have cracked at all, untill it was fired, sometime down the road,,,,case head failure, hot load, bolt lug wear, ect...all could have helped crack the action.
hard to say for sure,
iv had some 17,s that just fell loose,,,,others that took all i could muster to loosten them, from all 3 manufactures, worse ones seem to be early Winchesters, mc Guilla Gorrilla must have worked at Winchester back then..
i have found that the 1917 though very strong is actually very soft as compared to say a 1903, or Jap Type 99..
the last 10 years iv been doing some research on rifles that have failed, and some of the reasons why... so this poor girl goes into my log as a cracked 17...unknown why as of yet..
i have a couple 700 Remingtons with cracks, in the same area, both had case head failures, and had vented hot gases out in places you should push gas through,,,the 17 doesnt really have a gas excape area, one small hole, and back in the shooters face, heck a popped primer would ruin your day,,,most 17,s will blow the mag well down, and fracture the stock as well..
i think more then just a barrel install, made that action crack,...any shooter history??