Co2 Efficiency....

700 sounds a little low to me, even for a 98.  You should be getting over 1000 shots, unless you're a speed shooter.  If you shoot fast, that CO2 doesn't have time to recover (gas back up) and you start pulling liquid into the gun.  That'll make you loose CO2 extremely fast. 

Another thing to check when you get your tank filled.  Watch to see if the guy/gal purges your tank.  This is for two reasons, one to measure the tank "empty" weight, so he/she can fill it to the right amount.  Two, if the tank is warm, the liquid will convert to gas and use up some of your volume, thus you won't be able to "squeeze" the proper amount of liquid CO2 into the tank.  If they don't do this procedure, that would definately explain you 600-700 shots per fill.

trulyoldnavy wrote: Tippmanns are incredible machines that will often continue to work for long periods of time before showing signs of distress. Because of this many people often skip the post-play cleaning that is required of most markers. One result of this is a marker not performing up to its full potential (i.e. being a gas hog). When was the last time you fully disasembled, cleaned and lubed your marker?     One thing that greatly improved my efficiency was polishing the internals of the receiver halves. It's not hard to do, just a bit time consuming. I did quite a bit of it sitting in front of the TV on a lazy saturday afternoon. Good luck.

That is very good advice.