If you get bored with all this stuff, try designing an audio speaker box. Lots of math to play with there, but the bottom line is if it doesn't leak, it will work satisfactorily.
I have an M4 that I ported the living crap out of before I even knew why this was done. I figured it let the cyl fill faster and reduced "suck-back"...
I just measured a CA cyl at the shop and matched dimensions, adding a few more holes further back, tapering in size. So there are three holes in a row, largest one at the start of the power stroke. There are four of the hole groups going around the cyl. The porting effect is as amplified as it gets in this gun. This gun has a high-speed Systema motor, 170 spring, metal bearing spring guide, metal bushings, reinforced piston/head, and a Stainless steel cushioned cyl head.
How does this gun work? Terrible on semi. The bb will go about two feet before dropping. On full auto, yeehaw! It will spit a solid stream of hard-hitting pellets with very acceptable accuracy for CQB.
I was building a short gun anyway, but I have since learned that putting a long barrel with this gearbox results in a dog of a gun with lousy range.
