I guess I'm not sure what the point of telescoping brass is. Could someone explain it to me?
Since spring guns output a large amount of air slowly(unlike air guns which puts out air fast) you want the dart to get the full blast of the air. You need the dart to build up air pressure, by the time all the air is released. The telescopic brass is to prevent the dart from leaving the barrel before building up sufficient pressure.
Telescopic brass is when the brass size starts out smaller(where the dart is) and gets bigger with different sizes of brass. Usually, it starts out at 17/32 and then gets bigger with 9/16. Some people also nest 1/2 into the 17/32 to prevent the dart from going into the barrel.
Since cpvc is a very tight fit, it works mucht the same way, except without getting bigegr, which is whyit is also a very good choice on guns such as a TTG or an NF. If you do the mod correctly, cpvc gets the same ranges as brass, without having to blow the dart down the barrel, just push it in with your finger. With cpvc, you can ram the dart down the barrel to get better good velocity, and about 10 feet more range.
To sum it up, if you have extra time, and want a far shooting pistol, use cpvc and a ramrod. If you just want a fast shooting pistol, use nested brass,brass,or cpvc.
Hope that clears it up for you Nerfer16.