[Zack The Ripper]

Barrel length means very little unless the inner barrel is less than 250-280mm. You can tune barrel groupings very well based on cylinder size, barrel length, hop chamber, hop rubber, and BB weight.

However, generally speaking, a R-Hoped 455mm Prometheus 6.03mm bore tight bore barrel and a gearbox using a full cylinder is the universally agreed upon "best" barrel grouping setup. This is obviously not truly universal, but is a good go to if you want a guarantee for most builds. You could do this with a 14.5" barrel AR platform that has a 7" mock suppressor mounted to the muzzle to hide the inner barrel. It's a good base to work from if you want that look, or you can just go with a full length M16 barrel set.

Suppressors only muffle sound if there is foam in the can and there is a some measure of distance from inner barrel muzzle to suppressor muzzle - there needs to be space for the air to be dispersed. It's a noticeable difference, however not by a large margin. The cons to a suppressor is that your BBs may make contact with the inside of the suppressor and become detrimental to your accuracy. Suppressors are good for CQB or night games if you want an added element of stealth, but ultimately if you build a gearbox properly the gun should be very quiet as it is. Firing on semi using an already quiet gun without a foam suppressor will not be that much louder from 100 feet in the woods than the same gun with a foam suppressor.

If you want full stealth, get a foam suppressor and end your inner barrel at the barrel muzzle. If you want the best accuracy possible, have the inner barrel go right to the very end of the outer barrel/mock suppressor.

Make sure you get your gearbox shimmed correctly and get a quality motor that way your gun will run quick and QUIET.

For outdoors, get your velocity setup as close to 400fps as you can with hop up OFF, but don't go over as most outdoor field limits are 400fps. Use heavy ammo, 0.28g BBs or heavier; probably heavier. Heavier rounds are not as subject to air misdirection from wind, and heavier rounds tend to achieve a flatter trajectory from muzzle to target.

If you live in the GTA and want your gun made awesome, PM pestobanana here on ASC. Every gun he touches turns awesome.