In the 452 . . .
the bore is tight. Try pulling a snake through the 452 and then the 60, you'll see what I'm talking about. Because it is tight, and you force the bullet into the chamber with the bolt, it shoots most ammo well. If you get too big a diameter (>.224) it has a little trouble. Most remington stuff falls in this category. Federal and CCI are usually a little less diameter (~.223). Federal seems to use a little harder alloy, but the softer CCI seems to swell and fill the rifling a little better. Winchester Xpert and Dynapoints (haven't put the mic to them) look really slim. The smaller diameter is probably why your 452 likes them. Only one of my FIVE 452s, actually one 453, likes Winchester, though. They seem to be pretty consistant box to box, and, like you, I haven't had a lot of "pffts" (I liked that). I've shot at least 10 cartons through my Kimber .22 Conversion (won't feed big diameter stuff).
I know it wasn't the question, but since you're a 452 shooter, Federal Champions seem to shoot the most consistantly through the 9 452s shot by me, my dad, and my buddies. The Federal 550 Cartoned Copper Washed HPs and CCI Mini-mags are a damn close second. CCI Minimags sized to .223 give me my best groups . . . one slightly ragged hole at 25, one just slightly more ragged hole at 50. That's in my 453 and 452 Americans. This is for the cheaper stuff, of course. They all love Eley.
Now that I've read myself type and since you'd answered your question before I started . . . you're not going wrong with the Xperts . . . they stink in shotgun stuff, though.