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m102404 · February 18th, 2010, 20:20

Read Madmax's "Why it's important to match the cylinder to barrel...something"...thread. Although Madmax tends to get all physics and mathy at times...it's very well written.

In layman's terms (for dummies like me) picture this.

A car starts from a dead stop and moves 10ft...at the end of the 10ft it's not moving all that fast.

The same car is going 60KM/hr when it hits the start line...it may not be going much faster than 60km/h when it crosses the 10ft finish line, but it's still a heck of a lot faster than the time it start from a dead stop.

Now picture this....you've got a syringe with a straw on the end of it. That basically describes the piston/cylinder/cylinderhead/hopup/inner barrel of an AEG.

If you've got a BB right at the end of the syringe just before the straw starts...and the straw is really short. Then you slowly squeeze the the plunger and it moves forward, it compresses the air behind the BB and the BB starts to move...it'll dribble out of the end. Give or take a bit, when the volume of air that the plunger displaces matches the volume of air that the straw can hold...the BB moves far enough to leave the barrel. Any extra plunging/pushing of air is wasted.

Now...imagine you punch the plunger and it snaps forward fast...the same amount of air is displaced...but the BB is going to go out much faster.

Since you can't really vary the power that way in a AEG, you can accomplish the same "get the piston up to speed before it starts compressing air" by venting the piston. The piston won't compress any air until it passes the vent hole...so it's moving faster when it does start compression and the BB starts to move.

The BB doesn't really "plug" in the barrel...it's a loose fit...so there's no build up of pressure and then "POP" out goes the BB. It's a push of air that directly proprotional (in some magical mathmatic way) to the speed of the piston.

So...now picture the same ported cylinder but instead of a really short barrel...you've got a massively over long one. What will happen is the BB will get moving fast...but the piston will hit the end of the cylinder before the BB is out the barrel. No more moving air...BB starts to slow down and drag in the barrel. You can drop LOTS of FPS by doing this. One guy couldn't figure out what was happening and then cut 1" off his inner barrel...all of a sudden he picked up 150fps.

So to optimize things you want to get the piston moving as fast as you want it to, but still push enough air to get the BB out the barrel.

A cylinder with a port way up front is great for a MP5K...tiny short barrel. Want to get high FPS out of that and you'll need a really powerful spring.

A cylinder with no port works well with a long AK/M16 length barrel that needs a lot of air going through it.

Reverse the two and you've got sh*t.

So...you can play around with all this...but in the end it's just easier to go off a chart and pick the right cylinder for the length of your inner barrel. If you think that you're going to stick a 363mm inner in your MP5 and hide it with a silencer...go with a Type 1 cylinder. If you're going to leave it at regular length go with a Type 2.

If you mix it up a bit, it'll probably still work ok...you just won't have an optimal setup.

Hope that helps...and next time someone tells you to go read a stickied thread...go f*cking read it.

February 18th, 2010, 20:20	#7
m102404 Tys Trader rating Join Date: Apr 2006 Location: Toronto	Read Madmax's "Why it's important to match the cylinder to barrel...something"...thread. Although Madmax tends to get all physics and mathy at times...it's very well written. In layman's terms (for dummies like me) picture this. A car starts from a dead stop and moves 10ft...at the end of the 10ft it's not moving all that fast. The same car is going 60KM/hr when it hits the start line...it may not be going much faster than 60km/h when it crosses the 10ft finish line, but it's still a heck of a lot faster than the time it start from a dead stop. Now picture this....you've got a syringe with a straw on the end of it. That basically describes the piston/cylinder/cylinderhead/hopup/inner barrel of an AEG. If you've got a BB right at the end of the syringe just before the straw starts...and the straw is really short. Then you slowly squeeze the the plunger and it moves forward, it compresses the air behind the BB and the BB starts to move...it'll dribble out of the end. Give or take a bit, when the volume of air that the plunger displaces matches the volume of air that the straw can hold...the BB moves far enough to leave the barrel. Any extra plunging/pushing of air is wasted. Now...imagine you punch the plunger and it snaps forward fast...the same amount of air is displaced...but the BB is going to go out much faster. Since you can't really vary the power that way in a AEG, you can accomplish the same "get the piston up to speed before it starts compressing air" by venting the piston. The piston won't compress any air until it passes the vent hole...so it's moving faster when it does start compression and the BB starts to move. The BB doesn't really "plug" in the barrel...it's a loose fit...so there's no build up of pressure and then "POP" out goes the BB. It's a push of air that directly proprotional (in some magical mathmatic way) to the speed of the piston. So...now picture the same ported cylinder but instead of a really short barrel...you've got a massively over long one. What will happen is the BB will get moving fast...but the piston will hit the end of the cylinder before the BB is out the barrel. No more moving air...BB starts to slow down and drag in the barrel. You can drop LOTS of FPS by doing this. One guy couldn't figure out what was happening and then cut 1" off his inner barrel...all of a sudden he picked up 150fps. So to optimize things you want to get the piston moving as fast as you want it to, but still push enough air to get the BB out the barrel. A cylinder with a port way up front is great for a MP5K...tiny short barrel. Want to get high FPS out of that and you'll need a really powerful spring. A cylinder with no port works well with a long AK/M16 length barrel that needs a lot of air going through it. Reverse the two and you've got sht. So...you can play around with all this...but in the end it's just easier to go off a chart and pick the right cylinder for the length of your inner barrel. If you think that you're going to stick a 363mm inner in your MP5 and hide it with a silencer...go with a Type 1 cylinder. If you're going to leave it at regular length go with a Type 2. If you mix it up a bit, it'll probably still work ok...you just won't have an optimal setup. Hope that helps...and next time someone tells you to go read a stickied thread...go fcking read it.