Just got200 Winchester300 win mag brass that was plain ugly, case mouths were dented badly. I plan on shooting itwith FOD bullets before using it for any accuracy.

Most mass maunfactorers will send a notice to you now days due to productiion techniques,that the shells lips will be bend in production.Thats why they suggest on sizing and deburring shells before loading. vangunsmith

I just bought a bag of 50 .243 Win cases to load for a new rifle I just bought my son. Of these 50 I only had 4 with dented necks, which I thought was pretty good for Winchester.Except for this purchase, though, here lately (the last 2 or 3years)I've been buying better quality brass like Lapua, Normaand the new Nosler brass. I've been particularly impressed with the Lapua and Noslerofferings.

Yup and further you can plan on scrapping at least 2% of them as damaged beyond use.

Is this new brass from Winchester? Could they have been damaged in shipping?

No...it's the way new brass is sold. I get the same from Remington.

Maybe Norma or other is better but usually double the price.