Note that the M240 is a medium machine gun, not a SAW.
But, anyhow-
I also have a long barrel on my Classic Army SAW, and appreciate the accuracy and range it affords me. I like the 100rd soft pack ("nut sac") magazines because of the smaller size. I have mine outfitted with an M4 stock, rail handguard, ACOG, PEQ-2 battery box, and have performed some modifications to make the gun a bit lighter. This involved removing the gas knob, mount/cradle attachment point, carry handle, and front sight.
The Paratrooper stock was stupid heavy, and of terrible design, hence the removal and replacement with M4 stock. I did this 4 or 5 years ago after hearing about certain units performing these modifications to their M249s and Mk46s. Incidentally, a stock of this style can be had for less than $50 now for your airsoft SAW.
I have an upgraded gearbox, but it was so long ago I can't tell you what manufacturer produced the internals. Box is the stock CA.
I run Firefox 1600mAh 11.1v LiPo packs with Deans Ultra Plugs.
It runs like a dream, and at the hands of my teammates, has been to many national games.