Another poster said this:
Note this is the list:Simply throwing in a Type 0 cylinder regardless of the barrel length does not maximize efficiency of the system. The porting allows the piston to accelerate faster before it begins to compress the air (it can accelerate faster because there is no resistance from the compressing air, or the friction of the o-ring on the cylinder) This means when the piston hits the cylinder head (and when the bb should be leaving the barrel) it will be traveling at its fastest which will mean the bb will be traveling at its fastest for that particular system.
An under ported system means the force acting on the bb will stop before the bb leaves the barrel which leads to a decrease in velocity and could affect flight performance in other ways. An over ported (or lack of port) system means the bb will leave the barrel before the piston head hits the cylinder head traveling at its fastest, which means you are not optimizing the performance of your gun.
While over porting is better than under porting, it is not a good idea to just "throw the list out the window". If you want maximum performance, then that list is a very good start on how to do it.
Type 0 (No hole): 450-580mm
Type 1: Systema makes this one, it has a hole in the edge and is said to be for M4/M16/XM177/AK47. It is essentially a go between for the type 0 and type 2
Type 2 (4/5 hole): 364-460mm
Type 3 (3/4 hole): 227-430mm
Type 4 (1/2 hole): 110-170mm
This comment came about me saying OB parts are pretty much worthless for the price you pay. You get about a 2-3% increase for double the price in parts.
However, what the internet is spreading around is only true for a "slow" blow system.I agree that bore ups are pretty much worthless, but when you are talking about exceeding 580mm of barrel length, you need all the extra cylinder volume you can get. I also agree that there isn't really a need to go past 509mm barrels, but for the people out there, that still want the performance form the system, bore ups might be their answer.
AEG’s work on the “fast” blow system and this is why:
Example: How fast does it take for a 15rps AEG to release the piston and have the head slam against the cylinder head?
There is no “major” time issue here for acceleration and ports.
AEGs are "Fast" blow systems.
And at 300fps how far has a bb traveled in that time?
These effects reflect the totality of the system and again that is a fast blow system.
Most of us know that TM is the creator of the Modern AEG. In Japan they have a regulation they must follow. This is the ASGK Standard. Back in the 1990’s ASGK said you cannot have an AEG shoot a .20g bb faster than 300fps.
And the Japanese are the Japanese, very good engineers. All mechbox parts in an AEG is made to a standard and are ALL the same except the Nozzle and the Cylinder. The key is efficiency of mass production. If you keep all parts the same, you only need to modify one part to change the outcome.
Thus that is why there are holed cylinders.
If you put a non-holed Cylinder in a MP5K, velocity will go up. That will make them in violation of the ASGK standard. To counter the velocity increase, due to the shorter barrel. They used holed cylinders. This is the main reason why there are holed Cylinders.
So if you want a smarter upgrade that will not stress your mechbox. If it has a holed cylinder…upgrade to a non-holed one.