My .243 groups well with just about any ammo you put in it. Remington core locts group very well, but I just dont like the penetration they offer. I prefer Hornady and Federal 100 gr in factory ammo. I can hit the X at 200 yard pretty consistently with either of these. I would say grouping is under 2 inches at 200 yds, sometimes better. I have damn near touched a 3 shot string at 200 yds.With both. Hornady's blow through bone. I have had pass throughs on 200 lb hogs at over 200 yds, in the neck too. Seen my boy shoot a small buck through both shoulder bones at 200 yds using Hornady's I have dropped quite a few descent bucks with the hornad'ys, always complete pass throughs. Have done the same with the Federals. Not much difference i dont think. I just started using federal last year, they are a little cheaper than hornady's. I'll have to reserve total judgment till after this year, when i shoot some big 'ol boars with the federals.

PS
one bullet my gun totally dislikes, is winchester supreme silverballistic tips.
Really bad shooting. I was told it's cause of the molly coating.