Don't forget about a barrel. A barrel is the single most important upgrade for your marker.
I would recommend THIS for a first barrel with .685 or .689 being the bore size and 14 inches being the overall length. A very solid and reputable barrel for $30.
I also noticed you were asking what the numbers meant for air tanks.
The first set of numbers 68/4500 is the cubic inches(ci) of the tank, basically the overall size of the tanks air storage.
The second set of numbers 68/4500 is the pounds per square inch(psi) of the tank, basically the amount of pressure the tank is rated to.
With the tank you are wanting to get, 47/3000, you will be needing to get air MUCH more often than with a 4500 tank. Moreover, your tank is made of steel, vice carbon fiber, making the tank much more heavy and cumbersome.
Roughly averaging, your marker with a 47/3000 will get about 10 shots per cubic inch, meaning you will have roughly 470 shots before your tank is COMPLETELY empty. Taking into account that at about ~ 700psi on most high pressure markers/tanks is when you start to see a drop in pressure, you have roughly 400 shots before you start to experience drop off from your marker not getting enough air pressure to shoot a paintball at ~280 feet per second. Too put it into perspective, that is basically a hopper and *almost* 2 pods.
Carbon fiber tanks(4500s) average, with your marker about 15 shots per cubic inch. So a 68/4500 would at or above 1,000 shots off of a single fill before your tank is completely empty. When you again take into account that drop off occurs at about the 700psi mark, you'll get off roughly 8-900 paintballs before needing to refill. In perspective, a hopper and 4ish pods.
Again these are rough averages, some markers get far more from a single fill, this may be one of them. I'm simply trying to paint a picture for you so you can understand why 4500 tanks are much better than 3000s
That is at or about double what you would have for a 3000psi tank. a 68/4500 is also about or slightly shorter in LENGTH than a 47/3000, just a bit larger on the circumference.
Last but not least, steel tanks (3000s) need hydrostatic testing every three years, vice carbon fiber tanks (4500s) needing hydrostatic testing every 5 years.
Edited by AoSpades, 28 July 2014 - 05:43 AM.