In a nutshell, a good cheap paintball gun will satisfy all the following criteria, but it will have none of the fancy features of the more expensive models. When doing your research and asking people how they rate a paintball gun, keep the criteria in mind.

Reliability and durability

Even a cheap paintball gun should be reliable and durable. The paintball gun needs to take some heavy knocks and not complain, it needs to function in all temperatures, be able to load paint and charge up with air and fire without causing you problems. If a paintball gun cannot do this, it is a bad paintball gun. It is therefore essential to take a paintball gun for a thorough field test before you decide to buy.

Ease of operation

A good cheap paintball gun will be really easy to use. A good way to assess usability is to have a read of the manual. Does it look easy to use? Avoid paintball guns where you have to use more than one tool to adjust the paintball gun velocity, or where you have to take the paintball gun apart to adjust velocity. Again, a field test will reveal all you need to know about ease of use.

Precision and velocity

Fired at the same spot, the paintball gun should be sending balls to that target with reasonable consistency from twenty five meters. Try fixing the paintball gun to a tree so that it can't move. Then fire away and see how precise it is now that you have removed human inconsistency from the equation. If balls seem to occasionally fall short, then it looks like the chrono velocity, the speed with which balls leave the gun, is inconsistent and so precision is suffering. Velocity needs to be consistent and high enough to give you reasonable range.

Paintball gun paint

A good cheap paintball gun will work with any brand of paint ball. A good cheap paintball gun won't get all snooty if it's firing lower quality paintballs, but a bad one will often break the cheaper balls. This an important issue, since when you get to the play area, you often have little choice in the brand of paintball that you are given.

Weight

A good cheap paintball gun should be relatively lightweight. Keep in mind that you will be carrying it all day, running around and if it really takes the strain on your arms then it is no good for you.

A safety mechanism

A good cheap paintball gun will have a safety mechanism which will make the paintball gun impossible to fire.

Ease of maintenance and cleaning

A good cheap paintball gun will be easy to maintain, easy to take apart and easy to clean. You should not have to spend much time on maintenance or cleaning. Again, check the manual and see how easy it looks to maintain and clean. Avoid paintball guns that require a lot of oiling. For example, if a paint ball gun needs oiling every two hundred balls then this is going to seriously compromise your playing ability and your fun.

Aftermarket upgrades and accessories

A good cheap paintball gun will be upgradeable and will be compatible with accessories.