The bolts are sticky on all of them . I belive its the metal mix (nickel with steel). Gives great strength for receiver but does not slide smoothly with the bolt of the same material.
Oddly no mention of that in any literature of WWI I have read. 1903 is far smoother (though of course they had the receiver issue.) Worst WWII bolt in an 1903A3 is better.
It would seem to be a combat issue but again nothing said. Odd
Pure speculation that it was better then and age changed the surface chemically so not so great now.
That said, its miner for me, more a question than a curiosity and while I like shooting a great deal, I get a kick out of the 1917s. Something that just grabs me and those have my heart.