Finally received my replacement (refurbished) 600PF, and performing the slow turn of the MF ring, it's feeling gritty just like my previous one

So, either it's normal for it to feel like this, or I lost the lottery and this lens also has an issue. Could someone do a quick test of their 600PF and see whether or not there's a gritty feel to it during regular use? Like, is it smooth, then gritty, smooth again, etc? Turning the MF ring on my 100-400, it feels a lot better, though it isn't perfectly smooth either, so perhaps I'm being paranoid and this is just how they're supposed to feel.