winchester supreme vs. remington core loct
 

which is better at 120 yrds at killing a deer in .243

It wouldn't really matter.Just find out what the gun shoots the best and go from there.

Assuming accuracy is equal, which may or may not be true, I'd go with the more rugged bullet. Of your choices I don't know which that is. I'm of the opinion that the 243 is light for deer unless the bullet is meant for deer. That means a bullet constructed not to fragment into pieces.

Premium bullets are not needed for deer, so if a "green-box special" gives good performance on deer and they shoot fine, so much the better.

I've killed about 85 with the CoreLokt and 12-15 with Winchester PowerPoints in both the Supremes and the old white box...I got more reliable pass throughs and blood trails on lung shot deer with the CoreLokts...

I can't say the PowerPoints "failed" me though because I didn't lose any deer with them...

Inside of 200 yards just about any of the low cost bullets work...I'd look at the Federals as well...

From my findings on off-the-shelf ammo, many times my guns don't have problems with the Core-lokts performing good both in expansion, accuracy and over-all kill satisfaction. I do prefer customized ammo, but for the money and convenience, the C-L's do just fine.

iSnipe

I would aways use Winchester ammo over Remington in any situation. I have had a lot of trouble with Remington and never any trouble with Winchester. I just don't like Remington ammo.

Federal powershok
 

I shoot the federal powershoks in my 243. 13.00 dollars a box. Killed three last year withem, furthest was a huge doe at 140 yards another was a buck at 100 yards and the third was a little doe at about 60 yards. All pass throughs, the deer only ran about 15 20 yards. Bled like crazy.. Accuracy is great.. Try them if you can find them, they are real easy on the wallet also.. I killed them with corelokts aswell though... Now the hornady btsp shot the best out of my gun but they are 25 bucks a box..