There are fill chart calculators, the Marauder has a relatively small air tube and you can expect 75 psi drop per fill on that size tank. After two fills I was experiencing about 100 psi drop. When using a 4500 psi tank getting filled at the dive shop, I would sometimes only get a 4000 psi fill.this 500 psi less in an 88 cu ft. tank would mean 1/2 the fills as compared to the full 4500 on a 350 cc tank on the 25 Cricket with a 3300 psi fill. I would opt for a 22 Marauder for your pest bird shooting. I was a power nut, as I have places where I could not launch a 22 rimfire off the property if I tried. Tflatts demonstrated excellent shooting with a detuned Leshiy. The Marauder is easy to tune, and you can shoot a heavier pellet slower as not to penetrate anything. These guns pop up new on various sites that do not advertise here and can be found super cheap. Also Benjamin has a sale on Friday.
