It depends. Are we talking about a bomb built by a foreign state, or a bomb built by futuristic terrorists in a basement?
If it's the terrorists, anything is possible, because lord knows how they built it. In that case it's probably a dirty bomb, and anything you do to it will turn it into a dirty bomb, so the best you'll accomplish with your stunt is doing the job for them
If it's a large nation-state built bomb, however, shooting the bomb will, at worst, do nothing and maybe leak a little radiation, and at best, disable the bomb. I'll let you decide what exactly happens in this case.
I know you said that the markings on the bomb are in another language, but I'm going to assume they stole the designs from the USA, or at least have followed a development progress similar to the USA, in order to give you references on where we stand now with our nuclear arsenal.
We no longer use touchy explosives. The explosives used in modern nuclear weapons are some of the most stable explosives which can still be considered explosive, due to the 1968 Thule Air Base B-52 Crash. In that crash, one of the nuclear bombs being carried had a partial detonation, due to a fire destroying the controls and activating the explosive during an airplane crash. It became a dirty bomb, spitting crap all over the place. Cleanup was somewhat successful, but the biggest thing we got out of it was less sensitive explosives and fire-proof electronics boxes.
We no longer use touchy control electronics. “Until my death I will never forget hearing my sergeant say, 'Lieutenant, we found the arm/safe switch.' And I said, 'Great.' He said, 'Not great. It’s on arm.'” (1961 Goldsboro B-52 Crash). Two nuclear weapons on this plane crash nearly blew up. The first bomb completed it's arming sequence, but failed to explode because a single safety switch was switched off. The second nuclear weapon carried in this plane had also partially armed... but this one's switch was ON! The only reason it didn't go boom was because it hit the ground so hard it disintegrated before it could completely arm itself.
Our nuclear weapons are specifically designed to not work at all. "Bypassing a PAL should be, as one weapons designer graphically put it, about as complex as performing a tonsillectomy while entering the patient from the wrong end." Permissive Action Links. After all the close calls and near misses, President Kennedy put the kibosh on the slapdash weapons we had lying around. PAL refers to the arming and triggering systems used in a modern nuclear warhead; it requires encrypted arming codes, has intentional "weak links" in the system designed to fail safe in anything but an intentional detonation... it's designed to fail except when a very specific sequence of actions are intentionally taken.
Note that that complexity is involved in making it EXPLODE. It's very easy to make it not work with a PAL.
I doubt shooting the bomb is considered an intentional activity.
Ensuring that nukes don't accidentally explode was so important that the USA gave the tech to the Soviet Union. They developed their own system, but used the American system as a template. Ironically, the Nuclear Nonproliferation Treaty made it illegal for the USA to provide any guidance on how to safe weapons, an therefore they had to use a dodge to help France build their own PALs. China asked for data on PALs, but President Clinton said no, both for legal and security reasons (but I'm sure the security reasons could have been dodged). Pakistan refused to use USA PALs that were offered, because they fear a Kill Switch, but the NNT means we can't help them build a system they trust.
In the case of China, though, I'd expect even more paranoid bombs to ensure that only a central command order could launch and explode them; Pakistani bombs are likely proofed similarly to the USA, except without the full PAL style system.
In short, as another answer said, nuclear bombs are built to fail except in very specific circumstances. A bomb labelled in a foreign language would likely be the same, and if I was holding a rifle next to a bomb about to go off, and the only choices were to wait and explode or shoot and maybe explode, I'd take the chance.