It's not a Geo2, honest..
Join Date: Mar 2004
Location: London, UK
Yep, Geo efficiency isn't all bad - it just seems to differ widely from person to person for some reason.
Anyway, there are at least a few thing to do to make sure that you get the best from your Geo - more a matter of minimising wastage, rather than actually saving air.
First things first, make sure that you have a good paint to barrel fit. Planet used to supply all their markers (including the Geo) with a stock 0.693 barrel. This is a perfectly sensible approach in terms of making sure that the stock barrel can be used with any and every paintball you are ever likely to come across - you can shoot the smallest ball through a large bore, but you can't necessarily get shoot the largest balls through a small bore (as is fashionable currently, you can get away with a certain degree of underboring, but not large differences). However, this approach is not great for efficiency, as a small ball will not seal the air behind it in a large bore - some of the air burst will accelerate passed the ball and be wasted.
So, get a barrel that better fits the paint you use most often, or get a barrel kit. You could get the two bore upgrade pack for your stock barrel, which still isn't the best for the very small paint you can find now, but with 0.689 and 0.685 backs, is if nothing else a big improvement over 0.693.
Check for excessive blow back up the feed neck, and if you have it, try replacing the bolt tip o-ring.
Check the pin hole vent behind the o-rings on the can. There should be a noticeable hole through the can, but it should be absolutely tiny - just 0.3mm in diameter. If the hole is any larger, it'll waste air.
Screw the VVC adjuster screw all the way in.
Dwell tune - start at stock settings, chrono, and then reduce your dwell a little. Chrono again. If the velocity hasn't dropped, lower the dwell a little more, and re-chrono. Repeat until you find the lowest dwell setting that maintains the velocity you set. During this process, don't touch the HPR at all, just the dwell setting. Check that the marker is consistent and doesn't suffer shoot down in rapid fire. If it does, go back up on the dwell setting until shoot down is eliminated.
Remove the back check ball from the solenoid and check that it is clean and undamaged. Then check it's diameter - 4.00-4.10mm is optimal, but a little larger is fine. A smaller, or much larger, ball may not seal correctly, and you would lose air each time the solenoid cycled.
Check your whole set up - marker, ASA, hose, fittings, air system - for leaks, and eliminate them.
If at all possible, get full, cold, fills. Fill the tank as slowly as you can, and if you have the time, let it cool, and then top it up. The quicker the tank is filled, the hotter it gets, and the more the pressure will drop as the tank cools down. You can loose a fair amount of pressure on a very hot fill.
All of those things together, may not make your Geo especially efficient, but should at least make sure that you are getting the best efficiency it can offer.
One other thing to consider if you got a Geo, would be to install the Soft Touch (ST) kit. It isn't intended as an efficiency upgrade, but some people have found that Geos that have underperformed with the stock bolt kit have benefitted from the ST kit. Geos that perform well in the first place don't gain much in efficiency from the upgrade. Even if the ST kit didn't help you, you would still have the intended benefits of the ST kit (reduced kick, no issues shooting Reballs, eliminates cycling issues that can occur when shooting at, reduced velocity, and as incidental benefits, should be able to handle very fragile paint better) so it wouldn't be money wasted.
If you really like the idea of the Geo platform, but are still concerned about efficiency, then I would really recommend taking a long, hard look at the Geo2. It's more expensive, but I would say it is worth it. A number of changes have been made to increase efficiency, including a longer bore barrel with a smaller bore (0.689); a bolt kit with a sprung core, which closes off the air supply to the bolt before the firing chamber empties, and so saves a little air with each shot (the stock bolt kit in the Geo2 also has all the benefits of the ST kit for the Geo); and a new reg that maintains velocity down to a lower input pressure, allowing you to use more of the air in your tank before it needs refilling (the new reg also allows you to use LP, MP or HP output tanks without problems, and is fully rebuildable, with a reversible/replaceable seat seal - no more having to buy new reg pistons if something happens to the seal).
On top of that, it is a nicer looking and feeling marker (in my opinion anyway), you have the thick to thin grip frame and grips first seen on the Ego9, you have a new board with a larger LCD, adjustable back lighting and a new user interface, and you have E-portal compatibility. It's a better marker all around.