The vz. 58 is a rifle well-known for being easily mistaken for – but totally different from – an AK. Everything down to the locking mechanism, fire control group, and operating mechanism is different from the famous Kalashnikov, despite appearances. In fact, the vz. 58 rifle was a huge achievement for the relatively small country of Czechoslovakia (now the Czech Republic and Slovakia), as they had produced a weapon every bit as good as its contemporaries from the superpowers. Certainly, a gun’s merits can’t be boiled down to a simple mud test… But it wouldn’t hurt to see how it does anyway, right?
In mud, the vz. 58 suffers a familiar problem: Gunk gets into the fire-control group and retards the motion of the firing mechanism (in this case, a linear hammer striking a firing pin). Fire control and locking are the biggest vulnerabilities of any rifle in a test like this, and so the most critical factor is how well-sealed the action is at these elements.
Like with the M1 and the AK tests, a single mud test doesn’t prove the vz. 58 is a “bad” rifle, but it is an additional data point. In fact, Karl and I agree: The vz. 58 is a fantastic rifle, better in a lot of ways than the AK itself.
So far, though, the AR-15 remains the Unlikely Mud King.