Going from a 22" down to a 16" with the 243win you will loose almost 300 fps with 100 grainers, according to Quickload. Same deal with the 270win.

243win shooting a 100 gr bullet at 2,700 fps will harvest a deer humanely up to 300 yards. And the 270win with 130gr at 2,800 fps will harvest a deer out to 500 yards. Just ran the #'s in a ballistic calc and looked at where the bullet's energy drops down to 1,000 ft-lbs, that's where I got the 300 and 500 yards.

Factory ammo will be very disappointing regarding velocity in a 16" bbl.
I chronoed some Factory 243win loads in a 22" bbl and the velocity was 150 to 200 fps less than what the box claimed.