These one peice alloy Barrels are superb quality, with debured and chamfered finish, reccessed glue track for T Peice glueing.
The shorter 27.5cm barrel are specially made to suit the original M4A1 GEN8 barrel length, so nothing else needs to be adjusted. If you want the barrel to poke out the end to be covered by a surpressor cover etc, then go longer.
The SCAR V2, MKM2 and most others can use a barrel 29 or 30cm in length.
Alloy barrels are a good upgrade over the stock platic barrels of most blaster. There is only a few stock blasters that came with an alloy barrel. With these barrels being 7.1-7.5mm internally (manufacturing tolerence of .4mm), they are perfect for quality gels from 7-7.5mm in diameter. The barrel size can increase foot per second by as much as 30fps over a poor sized plastic barrel.
It has been proven that a longer barrel does increase the speed of the gel a small amount. So as they say....bigger is better
All barrels can be cut down if you wish, you will need to ensure a nice finish on the cut to eliminate issues of a poor cut finish damaging the gels.
These barels do not have the T Peice attached, they are sold seperatley to ensure you get the perfect combo. Use Shoe Glue or a light smear of thin rubber glue in the reccessed ring to ensure the barrel stays firmly inserted into T Peice.
To install an alloy barrel, you dont have to completely open a gen 8 gear box, just remove the few screws around the T Peice nose, pry the nose open just enough to pop the standard T peice out, then drop the new one in, tighten it down tight but not too tight, dont strip the screws, make sure the gear box casing is firmly closed shut before you screw together to prevent the screw mounts from breaking!! And your done.