Because of the small design of a BB gun it is not possible to change the air system. However if it's a pellet springer rifle, not a BB rifle, then in some cases it is possible to change it with a Nitro piston system. But this should be done by a professional air gun service. A nitro system replaces the spring piston with a gas piston tube. It usually cost around $130.
spring drives a piston that pushes air
When the rifle is cocked, a spring is compressed. Pulling the trigger releases the spring, which pushes a piston forward, The piston compresses air as it moves. The compressed air blows the BB or pellet out of the barrel.
The Nitro piston is superior to the spring piston in design, but Yes, it can be converted back to a spring in most cases. It is best to have it done by an "air gun smith."
If you are asking about a Nitro conversion kit. (Piston) it cost about $110 for the kit. If you purchase it already in the rifle it adds around $50 to the cost
The nitro piston replaces the spring piston. It's simply gas that is compressed inside a cylinder instead of a spring. You can compress gas. So each time you compress the nitro it acts like a compressed spring. you don't have to add more nitro each time you shoot it stays in the cylinder. Gas is more even as it expands so you get a steady thrust when the rifle is fired. A spring uncoils, giving an uneven thrust as it is released.
There are several air rifle shops around the country that (TUNE) air rifles. Check the web under" air gun repair" or "air gun tune" and locate a shop near you to have the modification done. Also Pyramyd Air (see the link below) sells a NITRO Piston to replace the spring in most air rifles.
Nitro has a few advantages over Spring. You can leave it cocked for a long period of time and not worry that it will loose it 's power. You have a more even release force with nitro ( A spring wobbles). There is not a spring to break or get soft over time. The power will always be consistent.
piston work of the compress air and fuel compression
After doing some research I discovered some unusual facts about the Benjamin Elite air rifle. Apparently it is made specifically for Dicks Sporting goods by Crosman air gun company (Crosman owns Benjamin and Sheridan). In truth It is a Benjamin Superstreak with a nitro piston powerplant instead of the original spring power plant. I own a Superstreak. First of all it is a powerful rifle. The Super streak came out in 2007 in a .177 and a .22 Caliber rifle but very quickly the .177 went out of production and the .22 Caliber ceased a few years later. Now it appears on the Dicks sporting goods page with a Nitro piston power plant. Like I said it is a huge rifle and I would not recommend it for a small person. I'm 6' tall and I find it to be a heavy rifle. It is a beautiful rifle (Made in China). Is it a good rifle, Yes!----- Is it an Excellent rifle?,--- well after lugging it around, I find I like a slightly lighter rifle to shoot with.The Dicks add calls it an Airsoft rifle. IT IS NOT A AIRSOFT RIFLE it is a pellet rifle, a very deadly pellet rifle.
You will have to take it apart. Each model is different so you will have to find a diagram of the rifle.
Gamo makes a dozen different rifles and pistol's. I find then to be of Very Good quality. I personally prefer the Nitro piston models over Spring. The new Dynamax (PCP) looks promising but expensive.