Spring-powered or air-cocking single-shot airsoft guns. Manually compress a coil spring by pulling back the slide or bolt handle, release the trigger, thus release the spring, the air pressure created in the pump cylinder blows BBs down the gun barrel. Spring guns is said to be more accurate and reliable than AEG and GBB guns.
Blowback action is when air expanded and push the bullet forward while the bolt was pushed to the rear due to triggering. The empty cartridge is ejected as the bolt travels to the rear. The compressed action spring recoil and drives the bolt forward to the original position. EBB: Use electricity to simulate the blowback action. GBB: use compressed gas to simulate the blowback action.
The numbers are the weight of BBs in grams. The weight of BBs affects how much energy is needed to fire the BB out of the barrel and the trajectory of the BBs. The recommended BBs' weight depends on the manufactory of each products.
A standard magazine can hold from 10 to 30 BBs. However high-capacity magazines, which are also known as Hi-cap, can hold about 100 to 600 rounds BBs. These magazine usually have a wheel at the bottom to draw BBs up into the "ready" tube by rotating manually. BBs in the ready tube will be drawn into the gun when fired. Usually a Hi-cap will make more noise when you move around because the BBs inside will bounce around and the user will need to spin the wheel occasionally to ensure enough BBs are drawn up to be fired. Standard magazines are apparently hold much less BBs, that you may need 2 or 3 of them during a game, but they make no noise. For the cost or airsoft players who do not like reloading, the hi-cap magazines are definitely a better choice.
Free-float (or just "floating" for short) handguards are designed in a way that they don’t make contact with your rifle’s barrel. They attach directly to a barrel nut which is secured to the upper. This allows the handguard to "hover" or "float" above your barrel. The less chance there is for the handguard to make contact with the barrel, the less chance there is for the angle of your barrel to be slightly altered. This bending, also known as warping, is the culprit that causes your accuracy to suffer. Free float handguards, on the other hand, don’t have this issue due to their floating nature. They have even been known to increase your accuracy in the range of .5-.75 Minutes of Angle (MOA).