I still have had great results with Winchester, but I prep it too. I run it through a FL die (the neck is resized, just barely off the shoulder) I ream the primer pockets, deburr the flash holes, I use a Sinclair VLD inside neck deburring tool. I also crimp all my loads with the LEE FCD. I had one new WW cases in the 300 WSM that I had to cull. The round would feed through the magazine, but just inserted into the chamber, it would not allow the Kimber 8400 Extractor to snap over it. I chunked it hard, far away from my sight, with muttered words of hate, mixed with relief that I had discovered it at the range, and not in the field Aargh! Can't stand that, ha. ( Did I mention I was OCD for reliability? )
Now, recently, I bought some RWS .270 & 300WM. I still ream the primer pockets ( it just flattens the bottom of the pocket) run them through the FL die, use the VLD deburr. I don't weigh/sort the brass, I also crimp them. Both rifles, with the loads they like, give "outstanding" accuracy! Winchester factory loads in both grouped two to three times bigger! For Me, I use alot of Nosler ( but not for the 300s) and for the WinMag I've had good luck with Jagemann and Sig Sauer. If a new, prepped case groups well, consistently, I will load 20-50 loads in new cases and set aside, just for hunting. I then use the fired cases for practice or trying other bullets I am just playing with.
I do nearly the same exact thing with my brass! Long live the Lee FCD.
So in saying you've had great results, are you saying your virgin brass loads group about the same as the once and twice fired?
I always do load workup on new brass, and it seems to work out sometimes and other time it doesn't... But I think that is because I'm a pretty poor shot.
Do you anneal at all? How many firings do you get on your Winchester brass?