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Two questions:

1. How long would a fired projectile take to reach going level?
2. How accurate could the gun be with the 1970s tech vs. 21st century tech?

> Two questions: 1. How long would a fired projectile take to reach going level?

What do you mean 'going level'?

> 2. How accurate could the gun be with the 1970s tech vs. 21st century tech?

1970s targeting and markmanship was very, very good. Add in that it could fire repeatedly and you could put a swarm of projectiles on an intercept that could hit a non-maneuvering vehicle far out.

Assuming they mean ground level (sea level)?

Ooh, I could see that, autocorrect error instead of unfamiliar term.

/u/phiggy if that's what you meant, then it depends. If it was fired in the direction of travel, it would have an increased apogee but would eventually slow down from atmospheric drag and re-enter but it could take years because it's dense.

If it was fired 'backwards' to the direction of travel, it would probably take a little under an hour to hit the ground assuming it didn't vaporize on re-entry (lead might not fare as well as another bullet materrial? I don't know what they fired). Going from memory, it was Nudelman 37mm that was adapted for use in space and a quick Google says that it had a muzzle velocity of just under 700 m/s. A re-entry burn for a vehicle in LEO is usually like less than half of that so that should be enough to put the perigee inside the atmosphere where it would slow until it was falling straight down at its terminal velocity.

The gun wasn't intended to shoot at the ground.

It was to prevent other spacecraft from getting close and spying on them.

They put up a secret project. You fly your satellite nearby to take pictures. They shoot your satellite.

thanks...that makes more sense. Any idea what firing it did to the orbital parameters of the satellite?

They fired the engines to counteract it.

That being said, they never did it again, so it probably wasn't effective. Switched to missiles.

I’m too close for guns, switching to missiles.

What's fascinating is how close we came to having a serious military presence in human spaceflight. The US were planning on launching the "Manned Orbital Laboratory" (MOL) in the '60s but it ended up being sidelined by improvements in spysats as well as budget overruns before it was finally cancelled. The US continued dabbling with military uses of crewed spacecraft through Skylab and the Shuttle program but for the most part it was pretty boring stuff. Meanwhile, the Soviets launched the Almaz series of stations in response to the MOL program. However, out of 3 stations only one was able to operate successfully. Also, as in the US improvements in automated surveillance satellites undercut much of the program's justification for existence.

But then you get to the '80s. The US has the Shuttle which performs both civilian and military missions, of unknown scope. The Soviets decide they need a Shuttle too so they build their own (Buran). The Soviets also respond to the bluster of Reagan's announcement of the "Strategic Defense Initiative" to initiate a program to build weapons platforms in space, starting with an enormous 80 tonne military station replete with a laser canon. This vehicle, Polyus or "Skif-DM", ends up re-entering during launch due to a malfunction in 1987, completely changing the whole arc of spaceflight history. Meanwhile, the Buran, launched by the same heavy lift rocket Energia, launches a year later in an uncrewed flight. The Soviets slowly realize that there isn't some magic to the Shuttle and it's actually not that great of a vehicle (notwithstanding the cool factor) so they don't pursue the use of it much, then the following year the Berlin Wall falls, 2 years after that the Soviet Union collapses, and 2 years after that the Shuttle-Mir program begins, with Russian cosmonauts flying on the Shuttle, Shuttles visiting the Russian space station, and so on, as a prelude to the ISS.