In the famous issue #25, Steve Rogers died. Marvel ran a three Act storyarc for the next several issues; until issue #42 to be exact, dealing with the death of Rogers and the assumption of the shield by James Barnes. Starting with issue #43, Bucky Barnes gets his own storyline as Captain America. The storyarc is "Time's Arrow" and what I like most about the storyarc are the covers.
Here is issue #43:

The cover is split from the early Bucky costume from during and just after WWII with Bucky holding a rifle. The other half shows the new Captain America costume - not showing any firearm. The background behind the title is split between Japan's flag and the USA flag.
Here is the next issue, #44:

This cover maintains the same split cover idea, except the left side is Bucky wearing his Winter Soldier uniform. Again, the non-Captain side is holding the firearm. This time the background is split between the Soviet flag and the USA flag.
Finally, the third part of the storyarc, #45:

In this shot, we see a unified Captain America and no firearm. The flag in the back is not quite the USA flag, but it could stand for it. Bucky is not, however, the main feature of the cover, but rather, the shield of Captain America is.
Anyway, I think this is a really nice series of covers. I think there is a lot of potential for Bucky as Captain America.