Remington semi-autos are spotty at best as to reliability. With 200-220 gr bullets a 30-06 does anything a 35 Whelen does, and does it better. In fact the Whelen gives you 300 WM recoil with no better performance than 30-06. I've never owned a Remington semi in 35 Whelen, but I've owned 35 Whelen in a bolt gun and Remington semi's in other calibers. I wouldn't go back to either.
The 742's with the heavy bullets in .30-06 are reportedly the ones that get the bolt rail chew. Run 150s and they should last longer.
7400s have bigger lugs (lesser # too) and supposedly are not similarly afflicted.
Have had minor chewed rail guns work fine, and pristine ones cycle flawlessly.
Sold one to a guy who claimed it jammed on him constantly. He brought it to the range and I blasted it just fine.
He was a big dude, and soft...........yup, pillow shoulder was the cause of the jamming.
Note, one 742 was mint when I got it. Cold shot was 1" high at 100 yds. Next ones from hot bbl were 7 to 8" lower (the hot ones under 1.5" group).
Suspect the dreaded Mini 14 type of barrel warp.
Neat gun, sad it was jacked up.........proly why it was minty.
.35 whelen...............fun stuff. I'd like a pump in that. Shot a 700 classic when they came out in it (buddy had one). 250's at dang near .338 winmag V.
IIRC chrono was a little big in std dev, he used some filler to keep powder charge situated the same and things tightened right up. Do not remember what propellant he was using.
The 750 in that............sounds like fun
Dunno how the new stuff is design/execution wise.........if the $$$ worth it on such a platform.
Heard quite a few 7600's have been rebored in the past to it. Evidently enough that they said they ought to do a factory version LOL