It's basically the same weapon, with minor variations. A rolling block uses a semi-circular breech block (the part of the gun that closes off the rear of the chamber much like the bolt on a bolt-action) that is locked in place by the hammer. When the hammer is full-cocked, it unlocks the breech and you can thumb open the breech to load a new round in the chamber. Rolling blocks were single shot weapons with a relatively strong action (for the time, this was low pressure black powder stuff remember) that fired pretty powerful cartridges. This and the Sharps rifles were the ones most used to hunt buffalo.
They are all weapons listed in the Pip-boy in the recent video. The player doing the demo scrolls down a rather large list and we wrote them down. I'll try to get more info on each by freezing the vid later.
I'm with whoever suggested that this is the Euclid C Finder, the targeting designator for the Achimedes II.
If there is a mp5 type smg held with two hands (which there won't be) I would be reeaal haappy. Maybe you can put some kind of arm stock on the 10mm SMG added with a silencer & reflex scope that makes it a two handed SMG . . That would be sick nasty!
I'm trying to figure out what I saw in one of the vids. It was an SMG that had sights like none of the other we've seen. It had a boxlike rectangular reciever, rear dovetail mounted in front of the reciever on the barrel and front post. You only see tha weapon in iron sight mode while the player is shooting it and then just a ghost of a look when the player drops it down from sighting in. The charging handle is on the left of the reciever. At first I though HOLY CRAP! IT"S A THOMPSON!, but the rear sight is completely wrong. I'll try to find it again and look some more.
I'm not sold that it's a 416. There are few visual ques to differentiate this and I doubt we'll be able to disassemble it to see if it has a short stroke piston. I agree with whoever said it looks like tha Cyote, a very nicely tricked out AR-15A3 used for varminting.