That's the first time anyone has asked those questions about one of my infantry weapons.
Anyway, the Barrel itself is probably around 600mm and yes, it would be finite.
Technically all of the Mass-Driver weapons of Abwehr can been taken apart with ease for maintenance since there are very few moving parts to begin with. It is a railgun after all. All it really needs is a feeding mechanism and the superconductor rails can do all the work themselves.
But since the friction of the rounds would likely wear down the barrel, I guess they should replace the barrel in it more than other weapons. The weapon is made of high-grade titanium, so it would probably weather the beating better than just weapons grade steel. Because of that, the barrel could probably last ~2000 - 3000 rounds? Just a guess-timate.