Round or flat receiver?

I'm planning on ordering either a 10FCP or a 12BVSS in 308 and I'd like to order the scope/mount at the same tome so that when I get the rifle I'll be able to toss the scope on it and shoot, but is there any way to tell if it'll be a round of flat rear receiver? Is that something that has changed over time and now all new ones are the same style? Or is it something ill just have to wait until I get the rifle to know for sure?

Thanks.

All the new ones are round back

Excellent, thanks.