A mole of CO2 is 44g. 4 grams/44 = 1/11 moles . A mole of any gas is 22.4 liters . There for you can expect to see 2 liters of gas. at STP. At 61 cu in per liter you can figure you get 122 cu in. 4 4 grams . A standard CO2 cartridge is usually 12 gm. so 366 cu in. That is close if you need the gas at room temp and pressure. If you need it at 100psi you will need 100/ 14.7 about 7 times that. (unless yo are using the CO2 as the motive force for a solenoid valve)
The delivery pressure of a CO2 cartridge depends upon the temperature and the required delivery rate. Figure you can get 400 PSI (as high as 800 PSI theoretically) easily if you pull it out in short bursts. It is the vapor pressure of CO2 from liquid to gas. That is why BB guns work so well. The pressure delivered remain constant until there is no liquid CO2 left. After that point you get a few shots as the gas pressure drops.