Bore-Up cylinders have a greater volume than standard cylinders.
This is due to a slightly larger inner diameter.

Bore up piston heads have a larger outer diameter to match.

WARNING! SCIENTIFIC KNOWLEGE AHEAD!

In another thread, I posted the formula for figuring the volume of a cylinder.
Specifically, it's: Radius X Radius X Pi (3.1415) X Length.

As you can see, since you are essentially squaring the radius in the formula, volume increases exponentially as the radius increases. In other words, a small change in the radius equals a large change in volume.

Example:
A six inch pipe, one inch long, has a volume of 28 Cubic Inches.
A twelve inch pipe, one inch long, has a volume of 113 Cubic Inches.

In this example, when you double the diameter, you quadruple the volume.

[/scientific content]

The purpose of a bore-up set is to provide a greater volume of air to push a BB down a longer barrel.

I do not recall specifically, but I think the bottom end to use a bore-up kit is 590mm. I could be wrong on that, though.

If you do go with a bore-up kit, make sure you buy the kit. I have heard some people have issues trying things like a Guarder Bore-Up piston head in an ICS Bore-Up Cylinder.

__________________

Last edited by Sparky_D; 08-23-2010 at 08:38 PM.
Reason: Because some people can't accept a typo for what it is...

I’ve been looking at the whole Barrel Suck phenomenon and I just can not accept it as given.
I needed proof. So I decided to formulate some calculations as a starting point.

I’ll cover a lot more in this post, so please read through it fully before posting knee jerk reactions to my hypothesis.

For the purpose of this, I need to clarify some terms. Most will know them, but just in case…

Definitions;

AEG: Automatic Electric Gun (airsoft)

Barrel Suck: The phenomenon that apparently occurs when an AEG piston begins retracting while a BB is still in the barrel, causing a loss in FPS due to the piston sucking back air from the barrel behind the BB.

FPS: Feet per Second – Velocity of the airsoft projectile

IPS: Inches per Second (FPS X 12) used for calculations within this hypothesis.

ROF: Cyclic rate of fire measured in Rounds per Second or RPS

My hypothesis:
Barrel Suck is a misnomer perpetrated on the Airsoft Community at large due in large part to certain active persons in forums across the world coining the buzz phrase with little more than speculation and guesswork and a great degree of “Technical Gobbledegook” to fool the masses into a perpetual belief that what they say must be true.

Here are some mathematical statistics and formulas that can be duplicated to match any guns specific performance values. This is assuming the AEG is in prime operating condition and NOT double feeding due to magazine or hop-up issues.

Test Bed #1 (Long barrel, Low FPS, High ROF):

Inner Barrel Length : 600mm (600mm X 0.03937 = 23.622 in, but let’s call it 24”)

FPS: 250 (about the lowest FPS for a decent gun)

Cyclic Rate: 20 RPS

Calculations:
At 250 FPS, it takes a BB 0.008 seconds to travel 2 feet (24”, or just over 600mm).
[1 second, divided by 250 feet, times 2 feet]

At 20 RPS, a BB is fired once every .05 seconds.
[1 second divided by 20]

Assuming Zero Point on our timeline to be the point where the piston releases from the sector gear, the BB exits the barrel at approximately 0.008 seconds, leaving 0.042 seconds before the next shot even begins to travel down the barrel.
[0.05 minus 0.008]

The BB is only in the barrel for the first 16% of the firing cycle.

Test Bed #2 (Long barrel, High FPS, Moderate ROF):

Inner Barrel Length : 600mm (600mm X 0.03937 = 23.622 in, but let’s call it 24”)

FPS: 400 (the golden number for many)

Cyclic Rate: 15 RPS

Calculations:
At 400 FPS, it takes a BB 0.005 seconds to travel 2 feet (24”, or just over 600mm).
[1 second, divided by 400 feet, times 2 feet]

At 15 RPS, a BB is fired once every .066 seconds.
[1 second divided by 15]

At Zero Point (piston release), the BB exits the barrel at approximately 0.005 seconds, leaving 0.061 seconds before the next shot even begins to travel down the barrel.
[0.066 minus 0.005]

The BB is only in the barrel for the first 7.5% of the firing cycle.

Test Bed #3 (Average barrel, Average FPS, Moderate ROF):

Inner Barrel Length : 363mm (363mm X 0.03937 = 14.29 in, but let’s call it 14.5”)

FPS: 350 (pretty standard for non TM stock guns)

Cyclic Rate: 15 RPS

Calculations:
At 350 FPS, it takes a BB 0.0035 seconds to travel 14.5 inches.
[1 second, divided by 4200 IPS (350 FPS X 12), times 14.5]

At 15 RPS, a BB is fired once every .066 seconds.
[1 second divided by 15]

At Zero Point (piston release), the BB exits the barrel at approximately 0.0035 seconds, leaving 0.0625 seconds before the next shot even begins to travel down the barrel.
[0.066 minus 0.0035]

The BB is only in the barrel for the first 5.3% of the firing cycle.

Based on these examples, anywhere from 84 to 94.7% of the time (while the gears are spinning) there is nothing going down the barrel!

Also busting this “Barrel Suck” myth is the actual function of the AEG gearbox..

Before the sector gear teeth can even engage the piston teeth, the tappet plate is disengaging the nozzle from the hop-up chamber thanks to the ingenious location of the tappet nub.
While the piston is retracting, it will draw air through the nozzle, but since the nozzle is no longer sealed within the hop-up chamber, it can not suck air from the barrel. Try sucking soda through a straw with the straw opening just millimeters outside of the liquid. All you’ll get is air. Your sucking has no affect on the soda, just like the piston has no affect on the BB in the barrel (if it’s even still IN the barrel).

Now, with all of that being said, there is a problem which occurs with improper cylinder sizing which will affect FPS, Accuracy, Consistency, and Performance.

This problem occurs when your cylinder does not physically have enough air volume to fully propel a projectile down the entire length of the barrel.

Typically, cylinders have venting holes at certain positions along the length of the body. This is primarily to minimize air resistance during piston acceleration after release in small to medium barrel lengths. There are many resources available to guide you to the proper cylinder type for your barrel length.

Putting a 500mm long barrel in a gun with a cylinder designed for a 363mm barrel is looking for trouble. Your cylinder will not have the sufficient air volume to propel the projectile down the entire length of the barrel.

Use the following formula:

Cylinder ID in mm X Cylinder ID in mm X 3.1415 (Pi) X Cylinder length in mm (to hole, if it has one) = Cylinder Volume in Cu mm

Barrel ID in mm (if you don’t know the ID, use 6.08) X Barrel ID in mm X 3.1415 (Pi) X Barrel Length in mm = Barrel Volume in Cu mm
If your Cylinder Volume exceeds your Barrel Volume, you’re good to go.
If it’s close, you may want to move to a Zero or Bore Up cylinder.

So, in closing, the phenomenon known as “Barrel Suck” has absolutely nothing to do with barrel suck. It is simply a result of improper sizing of cylinder type to barrel length.

__________________
Arguing with a troll on the internet is like wrestling in the mud with a pig. After a little while, you realize the pig likes it...

Quote:

Originally Posted by Knief

This forum doesn't exist to validate your bad ideas.