Weird

I have run into a few problems like that over the years and they can be a real PIA.
The remington ammo will chamber so it must have something to do with your
reloads.

Maybe you could have a bad chamber ??
Its odd that you would have marks on one side of the bullet too.
That is why I thought carbon buildup, but that would not happen in 20 rounds.

Have you checked what the col where the lands are with that bullet, Via a hornady OAL length gage ??
Wondering if maybe you have a short throat rifle.

My 308 sporter has a lot of freebore.