It would have to be a swap btw the .40 and .357 sig. Most pistols that are chambered in one can switch to the other easily with just a barrel swap, the mags can even stay the same. I know Glocks and XDs can swap calibers between the 2 with just a barrel. I assume that is the 40 rifle can handle .357 sig pressures.One problem w/ .357sig is potentially the pressures. However, the 995 IS rated for +p and +p+. 9mm(standard pressures) go up to ~33000 cup, Whereas .357sig goes up to ~38000 cup. So potentially you might could from that standpoint.
Then theres the issue of case diameter. The removal of chamber material to make it fit may cause enough of a reduction in strength to make it no longer safe for the higher pressures.
Also the .357 sig cartridge is significantly shorter than 9mm.