I have two guns both with scopes but the one w/ the lesser scope is my favorite gun so i am considering swapping scopes but I still need and want both guns to shoot accurately. If i do the scope swap, will it be necessary to have both guns bore sighted and then taken to the range to sight them in? I'm sure the answer is yes but I'm wondering how "close" the guns will be to being "on paper" if i swap the scopes and don't bore sight. Any idea?

Don't need a fancy gizmo to bore sight your guns. If they are bolt guns, remove the bolt, put on sand bags or your favorite range rest. Look through the bore at a target at 25-50 yards, adjust scope so the line of the bore and the scope are close. Fire a shot, adjust scope, fire another........ When it's where you want it, move to a hundred and fine tune. If not a bolt gun, set up a large target at about 25 yards, fire a shot, adjust scope, repeat. Shouldn't take more than a couple shots either way before you're moving to a 100.

Yes. Any subsequent changes require re-sighting to confirm POI and tracking when mounted on a new weapon. They may or may not be "close". No guessing or estimating... you MUST check it.

+1 on "bugsNbows". You need to start as if from scratch.

I do it all the time. Usually, I buy a new scope and take the old scope and put it on another rifle that I don't use as much or just give it to my son to mess with. I've been doing this over the last couple of years with rifles that I inherited a few years back. I use a laser boresighter to get it lined up on paper, shoot at 25 yards then go back to 100 yards. With a bolt action, as pointed out above, you can remove the bolt and look down the bore to boresight it.

There aren't any shortcuts. Just because your scope was sighted in on one rifle doesn't mean it will be any where close on another.

+2 for Bugs

Everybody here is right. The only exception to this is if you have multiple scopes for one rifle and utilize a quick-detach system to swap between them.