By default they aren’t. Overall, every expert is going to tell you that the Russian artillery is more advanced. They have laser-guided shells in 152 mm with the deviation of half inch at maximal range since 1980s. The US tried to obtain the technology but was banned from it by the Russian export control at the time. The alternatives are only appearing nowadays and at the cost of over $100k per shell, whereas the Russian is around $6-8k.
This is simply impossible, even with self-guiding munitions.
Initial charge, temperature of the tube, atmospheric pressure and wind will all cause variation in trajectory.
The M777 howitzer has a CEP of 5 meters with unguided shells, which is about as good as anyone can get without guided munitions, and about 1 meter is about all you'll get with guidance. Even a guided munition has to overcome all of the momentum and other factors needed to cut 4 meters out of the 5 meter CEP. You might get a tighter CEP only if you use a tiny shell where a lot of the thrown weight consists of the guidance system alone, but 1/2 an inch will still be impossible.
The Soviet Union designed some fairly good equipment, often much more clever and less complex than Western systems, like the helmet guided optics on some fighters that turned the air-to-air missile slightly to obtain a lock vs. the very expensive improved electronic auto-homing systems developed by the US.
But much of the top high-tech equipment were lab models that could be produced only in small quantities. Even now, the Iskander, which is a pretty good system, still has a high failure rate and relies on a specialized guidance computer toughened for acceleration and temperature that is made in the US. Russia won't be getting more of those.