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The compressibility of water is a function of pressure and temperature. At 0 °C, at the limit of zero pressure, the compressibility is 5.1×10−10 Pa−1.[29] At the zero-pressure limit, the compressibility reaches a minimum of 4.4×10−10 Pa−1 around 45 °C before increasing again with increasing temperature. As the pressure is increased, the compressibility decreases, being 3.9×10−10 Pa−1 at 0 °C and 100 MPa.

The bulk modulus of water is 2.2 GPa.[30] The low compressibility of non-gases, and of water in particular, leads to their often being assumed as incompressible. The low compressibility of water means that even in the deep oceans at 4 km depth, where pressures are 40 MPa, there is only a 1.8% decrease in volume.[30]

maths:
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Typical chamber pressures for shotguns are 75-90 MPa (11,000-13,000 psi); for pistol rounds 100-240 MPa (15,000-35,000 psi), although a few magnums are loaded to rifle pressures; and for rifle rounds 310-380 MPa (45,000-55,000 psi), with some extreme loadings reaching 450 MPa (65,000 psi). By the time a rifle bullet reaches the muzzle, the pressure acting on it has dropped to around 50-70 MPa (7,000-10,000 psi).

Where we get a range between 7,000 and 55,000 psi using the maximum psi and some sloppy math a gunshot can compress water by ~0.0000025%