A .270 with open sights will still shoot so I'm a bit confused by your question?
You saying you have two rifles, one a pump and other a bolt?
Want to put a new scope on which make, model and barrel length?
If you had two rifles exact same length but just different actions the 'reach' would be the same.
A bolt action .223 won't shoot any farther than an Ar15 just maybe a bit more accurately although some semis are tack drivers. But that's another thread.
Traditionally bolt action guns have always been the go to style for supreme accuracy but lately as I said some semi auto guns made nowadays as every bit as accurate. It's really a mental thing for target shooters. The lessor amount of things that touch the case or bullet before it goes in the chamber the more accurate that round is gonna be. This is why serious target shooter hand load each round into the rifle rather than allowing bolt to drag it out of an internal magazine. Like Remington 700s. They have an internal magazine but most folks will slowly roll each round into gun and slowly push it forward into chamber. A semi auto can be quite rough on each round as it strips it off the feed lips on mag and shoves it up feed ramp and into chamber. This is another reason why a bolt will be more accurate. You can use hand loads in bolts action guns but have to be careful when using them in a semi auto. Unless you put a harder crimp on the bullet it can actually get pushed back into case during feeding. Even a few thousandths back can increase case pressure to dangerous levels. Slowly pushing a hand load into a bolt gun doesn't do that. Hand loaders like to crimp their rounds just barely enough to hold it well but not too much. The easier it releases from the case the more accurate that round will be. Another reason is overall case length. On bolt guns you can size your round to exactly meet forcing cone and rifling in chamber. After a few tries and a marker you can size the rounds to where when fed into gun the rifling just barely marks the bullet shoulders. Now the round is set perfectly and sized properly to be the most accurate it can be. There will be no 'jump' from case into rifling. On semi auto guns and pump guns you have to watch overall case length in order to achieve proper function.
So as far as accuracy goes I'd say two equal weapons in caliber and barrel length just diff in action will most likely be the same. But the Bolt gun will have capability of being tuned into a proper target rifle by matching ammo or hand loading perfect size rounds for it.
Did that answer your question? If not sorry, I'm a bit imbibed and rambled on.....
HAPPY NEW YEAR!!!!