OP, the folks telling you that you already have all you need are giving you very sound advice and there are a lot of very experienced hunters and history out there to back up their opinions.
I've personally done my best to avoid the 270Win, not because it isn't a competent cartridge/caliber but "only'' because the diameter of the bullets is a ''bastard'' size and because I almost exclusively hand load, for several different rifles that have the same bore diameters, none of which are .277, I've mostly avoided it.
That being said, I used one, which didn't belong to me, exclusively on Bear/Deer/Moose for one season, using 130-160 grain bullets.
I found the 130 grain bullets to be a bit on the light side, the 140/150 grain bullets to be just fine for everything I shot and the 160 grain bullets I used for Bears exclusively to have a bit more recoil than I prefer to live with, but were very accurate and never did recover one, from more than 15 bears take under a land owners permit that year, the longest shot being just over 150 long paces.
The same thing happened with the Deer and Moose, with the 140-150 grain bullets, shots were just under 100m and the bullets were placed through the boiler room appx 10cm under the spine. The bullets hit ribs going in and exiting. Neither animal, Mule Deer and Canada Moose went more than 20 yards before dropping.
The White Tails were taken with the 130 grain bullets, Nosler Partitions, for just over 2900fps. Both bullets expanded perfectly.
The animals didn't require a second shot as they were both visibly well hit.
One was around 75 meters and the other was just over 150 meters. That's almost point blank, which seems to be right in the average ranges I normally take game.
Both of those partition bullets hit bone. The first one hit middle of boiler room. Hit a rib going in expanded beautifully from the damage to the internals and hit a rib on the way out, then caught up in the hide, no exit hole.
Very similar performance on the second Deer which was twice as far out.
Nothing at all wrong with the performance of the Noslers. I just like a bullet that goes through and through, allowing the vacuum effect trailing the bullets passage to do what it does best.
If I were told the only rifle I could have was chambered for the 270Win, as long as I could use ''good bullets'' 140 grain - 150 grain weight. I wouldn't have anything to complain about.