Editor's Note: This is reprinted from the Popular Airsoft Magazine March 2008 issue and at Warfreaky.com. An AEG’s accuracy is an important factor for both sniper and assault role weapons. No matter how high your FPS is: if it doesn’t hit, it’s not a hit! Your airsoft rifle will never be as accurate as the real thing, but the following tips will improve your accuracy and groupings.

The first advice you’ll hear from most people to increase accuracy is switch to heavier ammo, like .25g up to .43g. Heavier BBs won’t be affected by wind, but will also significantly reduce the range and power. You can offset this by upgrading your FPS, but not everyone can upgrade above 328 FPS or use ammo heavier than 0.2g. Besides, that’s for another guide.

Compression

If your FPS isn’t consistent your BBs exit in different velocities, fall on different ranges, resulting in bad groupings. FPS deviations of +/- 10 or more means there might be air leaks in your gearbox’s compression. These leaks can be remedied without much cost by creative gunsmiths who use teflon tape, glue, and other sealants. Most of the time only worn o-rings need to be replaced.

The airseal nozzle is the first and only upgrade part I’d recommend. Check your nozzle if it has an o-ring inside (most china-made AEGs don’t); if it doesn’t have one, replace it immediately. It is commonly reported that replacing this results in at least 10 fps gain, it’s worth it at its cheap price (~US$7.00) so get the best branded stuff that’s compatible with your gearbox. The metal ones have no advantages over the ones made in plastic, by the way.

Hop-Up

Again, for the hop-up rubber and bucking get the best branded stuff available (US$6.00-US$10.00) since they're relatively cheap anyway. The hop-up system itself is irrelevant: one-piece, two-piece, metal, or plastic, these give the same performance unless damaged or misaligned. Better just save the money for something else.

Tight-Bore Inner Barrel

Now it starts to get tricky. The inner barrel is the single part that contributes the most to your rifle’s accuracy. The most bang-for-the-buck barrels are from EDGI, which you can get for US$20.00-up depending on the length. He uses brass (also used in airguns) and can customize for any length, inner diameter, and even outer diameter. Tanio Koba twist barrels are interesting, the rifling twists the air pushing the BB for greater range and groupings. These twist barrels are designed to work for a certain FPS (~328 or 1J) but sadly expensive. Here are some factors to consider when choosing an inner barrel:

Material — brass is very easy to polish; the inside surface needs to be as smooth as possible and brass allows this. Steel is stiff and resists flexing, which maintains good groupings during full-auto fire, but is also resistant to polishing. You can use a brass-steel inner barrel, or use brass inner barrel in a steel outer barrel (making sure that the barrel fits snugly).

Inner Diameter — the smaller the inner diameter gets the more accurate your shots get, but this also largely depends on the BB you’re using. Personally I prefer the 6.04mm for a compromise of accuracy and reliability; it’s safe to use most brands of ammo with this. The 6.03mm are for higher-grade ammo like KSC. The 6.02mm and smaller are for the smaller-diameter ammo like Excel.

The inner diameter should be small enough so air pushed from your gearbox will be concentrated on the BB, but large enough to let the BB pass without resistance. The increased airflow efficiency helps with consistency and also yields additional FPS.

Length — longer is better, but just get the same length as your stock inner barrel. If you change the barrel length, make sure to also change the cylinder type in the gearbox for matched air volume. Too much air volume from the cylinder will push the BB even after it has exited the barrel, changing its direction and that’s bad for accuracy.

Don’t just saw off the barrel to shorten it. The end has a precise crater-cut or crown that keeps the exiting air consistent.

Suppressors create air turbulence when BBs exit, and sometimes the BBs hit the foam inside. Make sure that the exit end of the inner barrel is no more than one inch inside from the exit end of the suppressor, or don’t use suppressors at all.

No Gearbox Stress

Unlike High FPS and High Rate-Of-Fire builds, upgrading for Accuracy won’t add wear-and-tear and higher maintenance costs. You can easily combine this build for High FPS + Accuracy or High ROF + Accuracy, but remember High FPS and High ROF don’t go well together.