Having replaced a lot of "shot out" barrels over the years, I would think it would take a tremendous number of rounds to shoot out a MZ barrel. With CF rifle and pistol, jacketed bullets tend to wear on the rifling more than lead. A lot of my customers are competition IPSC shooters and will wear out a match grade stainless steel pistol barrel in one or two seasons. Shooting jacketed bullets, the barrel life is generally limited to about 30,000 rounds. I have had some .45 ACP's that were shot with only hardcast lead that went 100K rounds. As pressures and "overbore" calibers get pushed to the limit in rifles, barrel life really takes a dive. Some of the worst are overbore rifle calibers that use long heavy bullets. Like the .22-284 with 80 gr. VLD bullets. 500 rounds?

As I see it, the lead bullets combined with relatively low pressures and zero overbore is going to make a MZ barrel last a long time. The part of the barrel (other than the breech plug) that I would expect to wear out first would be the muzzle end - from all thebullet starting andseating necessary with each shot. I'd be surprised if MZ barrels were particularly prone to the same classic throat erosion that plagues CF rifles. I also think swabbing the barrel in between shots is going to make it last longer. As each bullet passes over the gritty residue left behind by the previous shot, it is bound to have an abrasive effect over time.

Just my thoughts, as a gunsmith. I have no practical experience to back this up, though. Maybe some day I will shoot out of one my smokepoles, or get a shot-out one in the shop that has a well documented history.