IMHO - Skip springers and go directly to PCP. It is a very smooth transition from rimfire to PCP. Better accuracy too. I spent many $$$ on Fine German Springers over the last 40 years and even my most modest PCPs will out shoot and out power them all. Fire away...I don't care.
After hand pumping for years, I bought a Rovair compressor for direct filling. Game changer. Low maintenance, compact, and simple to use. A decent compressor is probably the most important component of your PCP arsenal...
Just for kicks I put a red dot on the Diana Stormrider. I also wanted to maintain the open sights for really close-up pesting. It works! When I want open sights I turn the red dot off. Funny thing, I'm almost as accurate with the open sights as I am with the red dot at 20-30 yds. Fun experiment.
I'd send it back. Something is messed up. That shot count is low compared to my stock two year old 2240 and Diana Chaser. Both of those get 40+ decent shots. I'm also getting 500 fps with 11.9 RWS Hobby. Put the $ in a Diana Chaser if you really need a cheap Co2 gun. The 2240 in stock form...
Unless your ground squirrels are the size of raccoons, I think my 26 fpe Stormrider ($220) would do nicely. It shoots JSB 15.89 at 850 fps. No, I wouldn't take shots at 175 yds, but out to 50, sure. Walk and shoot.