What cylinder should I use!
 

I was told when I converted my m16 to an m4 that I would need to change cylinder in my mechbox to a ported one.
Is this %100 nessasarry what is the difference between the two?
thanks again...Jonney:D

Yes you need to change it to an unported cylinder.

A ported cylinder has a port cut through its sidewall (a non-ported cylinder is just simply a tube). As the piston head passes rearward past this port/hole, the "suction seal" that it creates is broken. If you're firing in full auto and you get "suckback", you'll actually get a very low FPS and your shots will be horrible. Essentially, your bb is getting sucked back down the barrel before it leaves the muzzle.

It's a balance of ROF and barrel length. ROF is affected by battery size/voltage, spring stiffness, motor and BB weight.

If you have a super short barrel it won't matter, because the bb will be gone and out the barrel before any suckback starts. But if you lengthen that barrel, lighten the spring, hook up a big battery on a turbo motor...and you will get jams and erratic FPS.

So...to properly answer your question, you'd need to specify your motor type (+age, condition), battery, barrel length (but we can assume you're using a stock M4 length...a mm here or there doesn't matter), spring type.

But the shorter answer (and good for you if you got this far in my post...most stop reading long before the end) is...swap the cylinder to a ported one and don't sweat it from that point forward.

You should have no problems going from the m16 length DOWN to the m4 length (assuming the cylinder is the proper one for the longer barrel - probably is). I do this all the time with my m4/SPR with no serious side effects except *maybe* some fps loss - I just keep in the non-ported cylinder and swap inner/outter barrels around to whatever suits my fancy that day/week. You won't experience suck-back this way; possibly the other way around if you use the ported with the long inner barrel.

I tested the ported cylinder theory twice; here's what I found:

- G&P m4: LOST ~15 fps by switching the proper ported cylinder for a non-ported cylinder.

- A&K m249: Switched the improper non-ported cylinder for a properly ported one and saw NO fps change.

No, he needs to change it to a ported one.

Yeah i run a ported cylinder with a tightbore 6.03, 363mm inner barrel. M120 spring, EG1000 motor.....fps is pretty consistent.

My bad, should've read more closely.