Go to pyramidair.com
They are THE authority on all things air rifle, be it multi pump (like the Crossman 2100) or spring air powered rifles (springers as they are more popularly called) that use a high strength spring to suddenly and forcefully compress the air in a "firing chamber" to propell the pellet, and PCP rifles or Pre-Charged Pneumatics that carry a high pressure reservoir of air to give you some rediculously accurate and powerful shots. You can spend as little as $70.00 all the way to high end PCP's that run over $1500.00. Wal Mart actually has quite a few Spingers from around $99.00 up to over $250.00. Springers require much more PRACTICE to learn to use correctly and can really make some fine marksmen question their abilities if they don't hold and shoot them correctly. (google the "artilery hold" for shooting springers.) I have a Gamo Big Cat in .177 cal. that I paid $89.oo from Cabela's on a refurb clearance and had it modified to the point where it can, and will shoot as consistantly and accurately as springers many times its cost. There can be a lot to this but if you go to pyramidair, you'll find all kinds of info and even tutorials that'll get you headed in the right direction and their prices are very good too. Good luck.