2000psi safe?

[c19o]

Safety will be my number one priority in this project, I see what you mean about the rams now.

[DYI]

The rams wil be massive. I hope you have access to some large (i.e. >3" diameter) hydraulic tube. Hardware store variety stuff just won't cut it for this.

If you are serious about completing this, here's a good idea:
Use 4" tube for the pump tube, and 1" tube for the piston tube. This would give you a compression ratio of ~16:1, and you would only need a single stage, making calculations simpler, along with increasing efficiency, and decreasing final size. Or even 4"---->2"---->1" so that you could incorporate a bend and decrease length. Expect to pay a LOT of money for 4" hydraulic fittings. Leasing a large nitrogen or helium tank will be cheaper, and provide a larger volume of gas at the same pressure in less time and consume a fraction of the space.