lr 308 bolt rails

[bread]

So, I decided to try to design (more like modify) a short stroke gas piston system for an lr 308. I know stuff like this already exists, I'm not trying to make this to release it as a product, I'm just doing it for myself for fun. Just trying my hand at some engineering I guess. Anyways, I have a question about the bolt "rails" for an lr 308. I don't own an lr 308, I only own an ar-15. I've been using cad models from new.rifleconnection.com and I'm not sure how much I trust them. Looking at my ar15, there are these kind of wings inside the upper receiver that the bolt rides on. These aren't present in the cad model for the lr 308. Now, I know that the lr 308 and ar15 are different guns and it's not just a scaled up version of the ar15, but looking at the cad model, it looks like there is nothing for the bolt to ride on other than the feeds lips of the magazine, which doesn't seem right to me. I'll include a picture of the rails/wings (whatever you want to call them) in the ar15 I'm talking about, and a picture of the cad model and how there's nothing for the bcg to ride on. Could anyone possibly send me a picture of their lr308 upper in a similar angle so I can see if there's any bolt rails in there? Thanks.