So one of the most commonly overlooked part of making your aeg shoot better is the bb's you use.

Quality bb's, this subject varies from person to person, group to group and even state to state. However, there is a pretty much set list of what is a quality bb, and what isn't.

Quality bb's, Airsoft Elite, Bioval, Tokyo Marui, Maurzen, Marushin, Toy-tec, Excel, KSC, Super grand masters and ect. I know there are others, but that is a short list off the top of my head. I personally use TSD, as they are decent for price vs. quality.

Tightbore vs. BB
While many people want tightbore barrels, you have to realize that your tightbore will greatly reduce the amount of bb brands you can use. This varies, however this is especially important once you reach the 6.02-6.01mm diameters. Only the highest quality bb's will work. Your average wal-mart bb will not work in barrels even as small as 6.05, and often causes jams.

FPS vs. BB's
This section is very commonly underestimated. To acquire the best shooting results you need to use the correct bb for your fps, and set up.
General rule of thumb
330fps w/.2g and under = .25g bb's
330fps w/.2g and over = heavier, generally .28g bb's
400+ w/.2g and over (sniper rifles/DMR's) = .29g-.36
500+ w/.2g and over (uberl337 snipers) =.36g+

Now, you might be saying "but marsden, what about .2g projectiles? and isn't .28's wayyy to heavy?" Well, not really. This rule of thumb is for if you are making a gun that you are trying to obtain maximum accuracy (so if I have just hi-caps and want to hose, .2'g are the way to go).

Take this analogy, its the best one I've heard, and thank you Bill from Airsoft Radio for it. "Shooting bb's is like throwing marshmellow's into the wind, add a little weight and it will make a big difference."

So then you might think "well won't a .2g bb shoot further?" This is a common misconception. Following Bill's line of thought, and basic math, you find that while .2g bb's have higher muzzle velocity, they don't maintain that FPS for long. After being fired, a .25g projectile will surpass a .2g projectile aproximately 15-20 feet from the barrel while firing at the same energy. Will post charts on this later.

Wind vs. BB's
One of the biggest differences in Airsoft vs. RealSteel, is the bullet drift. This is primarily due to the weight and shape of bb's compared to real bullets. This is where the benefit of heavier ammunition comes in, .25+ bb's are much less likely to stray than lower weight bb's.

Sniper's
This is probably the biggest quandry I have in airsoft. People that are rocking sniper rifles, with 450+ fps and then using .2g or .25g bb's. At higher FPS the Bill theory gets expotentially higher. Realistically, 400fps w/.2g of 1.2joules of energy should use a minimum of .29g bb's to obtain the highest accuracy and also the most range from your gun. The higher weight bb's also increases the "felt" bb strike, which for snipers/DMR's is crucial in making them worthwile. One of the most frustrating things with sniping is people not feeling the hit, heavier bb's will definately help with this.

Over lubed bb's
This is a topic that we've had discussions on a lot lately at airsoftia. Bb's that come from the factory with a high level of lube, also known as "slick" bb's actually will provide you with a less responsive hop-up. The reason for this is the balance that must be achieved from the hop-up unit with providing grip and letting the bb pass through. Because slick bb's have less ability to allow the bb to grip, you get less hop-up. This can result in lower range and fps.