The first AR photo is a 458 socom, the silencer bore is about .520" to ensure no baffle strikes. The second AR photo is a 5.56 NM. The end cap is cone shaped like a baffle. Sideways it would look like the letter M. The bore is about .28" and the end cap opens up to about .65" on the outside to reduce weight. I care more about accuracy than suppression, so I give myself some more "oops" room than some others think is required.
Ranb