Super Soaker Central

The pump limits the gun. All of the power of a good water gun enters through the pump and out the nozzle. But how much power could be inputted into a gun? The manufacturers like Hasbro and Larami were kind enough to leave small hints as to what pump forces they designed for. The following table has taken information about the pressures within a fully charged stock gun to extrapolate the maximum force needed to pump.

Gun	Pressure (psig)	Stroke (in.)	Diameter (in.)	Volume (cu. in.)	Force (lbs)
SC 600	22	6	0.591	1.648	6.041
CPS 3000	22	7	0.596	1.953	6.137
SC 500	26	6	0.580	1.587	6.875
CPS 1000	23	7	0.623	2.136	7.018
CPS 1500	22	7	0.666	2.441	7.672
XP 110	40	6.75	0.578	1.770	10.487
XP 70	40	6.125	0.585	1.648	10.760
CPS 2000	45	5.875	0.640	1.892	14.490
XP 250	45	6.5	0.750	2.872	19.990
XXP 275	45	6.25	0.899	3.967	28.559
CPS	23	6.600	0.611	1.953	6.749
XP	42.5	6.406	0.703	2.564	17.449

The final two rows list the averages for CPS guns with the exception of the CPS 2000 and the XP guns. The CPS guns do not require nearly as much force to pump because their pressures are much lower. However, the XP guns do require much force to pump.

In a conventional APH-style design, the gun is limited by the pump. Taking the forces from the chart as the forces that the manufacturers believed suited users, we can see one thing: 1/2" PVC pumps can get higher pressures that 3/4" PVC. Some simple math tells us that a 3/4" pump can only generate up to 32.7 psig with this these limits; a 1/2" pump can generate 57.4 psig.

It seems that the manufacturers designed their air pressure guns to take on average about 18 pounds of force on the final pump. This fact can be vital when designing a gun.