what is the diffrence?

[ThunderCactus]

Originally Posted by plaugue

So if your gun was 6mm and you want to make it 8mm only the bearings and bushings need to be changed or does any other internal need to be upgraded.will this have any effect on reinstalling the gear box back into the gun ?

You'd need a CNC machine, accurate locating ability, and I'd use a 3/16" 2FL EM for aluminum to enlarge the existing holes.