Why Do long and/or Ported Barrels Sux Gas?

[e1ement5]

I have read a number of Posts that claim that long and/or ported barrels suck, or use more, gas then shorter non-ported barrels. Why is this so? I have given it some thought and I don't see the logic behind the claim?

Thoughts or explanations?

[Load SM5]

Some of the gas used to propel the ball is lost out of the porting. You have to turn up the pressure to compensate for the lost gas by adjusting the velocity up to achieve the 300 fps. you got when you were'nt wasting air out of all those little holes. Hope this makes sense, I'm a little tired.

------------------
Black vert.feed E-mag
68/4500 Dynaflow
12" Freak

[magman007]

ok per say thay dont actually use more gass to propell the ball, the gas as you know escapes out of the barrel right? well tht gas also proples the ball, porting allows the gas to escape out of the barrel, this inturen means the ball is not bieng pushed the whole way out of the barrel by all of the gas, this inturn makes you turn your velocity up a bit more allowing you to fire at a higher gas out put be cause you want to get to your maximum velocity am i right? if you are supposred to shoot 260 your gonna want to shoot 260 am i right? you dont want to go out there with a boom stick shooting olny 255 do you? you are olny shooting 255 with your boomy comparedto youe old crown point cuz you loose gass out of the porting.

------------------
you ever notice how elves do everyting???

[FeelTheRT]

http://www.automags.org/resource/tech/tomstech/01_barrel_eff.shtml

Tom's Tech Tips isn't there just to look cool.

[PyRo]

Ok, I belive it was miscues who came up with this example.
Imagine you are drinking through a straw. Now poke holes in the straw. What happens? The same thing applies to barrels, you loose air through the porting, requiring more air to get the ball through.

As for barrel length.
You have 2 barrels
=============
and
========
The ball is propeled down the barrel, by the pressure behind it. As it gets further down the barrel, the air has more room to expand, lowering the pressure. When teh pressure gets to low, the ball starts to decelerate. To prevent this deceleration, or to compensate for it you have to turn up your velocity more to get the same fps.

[shartley]

I may have missed something... but from reading what Tom wrote, can it be safe to say that most of the arguments on this issue are irrelevant?

My thoughts....

Again, correct me if I am wrong, but there seems to be an effective acceleration distance. And this distance is the same no matter if the barrel is 8 inches or 18 inches. Anything AFTER that fixed acceleration distance actually has NO effect on how fast (or efficient) the ball is propelled?

So the straw theory is not quite fitting for this discussion since one uses suction and one uses propulsion... and the effect of things traveling through the "tubes" is going to be different simply because the manner in which they are moved is different.

Also, from what Tom said:

The next question we need to ask is, how far down the barrel does the ball have to go before the pressure gets to low to do anything useful? That answer is 8-10 inches.

[cphilip]

Nope! Wrong use of what "efficient" is here. I think (pretty sure) he (the author of this post) is referring to total volume of air each shot as used in relation to efficiency. "More Efficient" being measured as using less volume of the air in the tank so therefore more efficient use of the tanks total volume. Not "efficient" as in "accuracy"
You will use more total volume of air to push a ball down a ported barrel and still achieve 280 FPS (and then recharge the chamber)as compared to a non-ported barrel. Because it takes more air to fill the void/leaks etc and produce the same effect that being 280FPS as the ball leaves the end of the barrel. Simply being because you will have to turn the velocity adjustment up to still achieve that 280 fps with a heavily ported barrel. I think that's what he means by efficiency. Total volume of HPA used per shot being more or less.

[shartley]

[cphilip]

That's true. But I believe I was on target by what he really meant by "Efficient". He wanted to know efficient use of the gas per barrel type...irregardless of accuracy. Course if they both leave the barrel at 280 fps the distance will be the same. Pretty much. Total "overall efficiency", which has so many other variables we are discounting for the purposes of this simple measure of "efficiency" is, as you say, a whole different beast. And of course if one can achieve all three...Gas efficiency, accuracy and maximum distance. Boy howdy! is that the Ricky or what! It's a careful balance and some compromises have to be made. And let's not forget trying to do it quitely too! Everybody wants that too. Throw that in and we really got something that's going to require some real compromises.

Sheesh! How do this all work anyway!!

Oh... and that is probably true after 10 inches or so it's a whole different and lessened effect. Although some feel its still accelerating all the way to the end of the barrel. I've never done any research on that point so I couldn't say.

[This message has been edited by cphilip (edited 08-24-2001).]

[shartley]

[XspyX]

This is a Deep Blue kinda thing...too much readin for me.

Yeah, I have an 18" barrel.

I don't care how much gas it sucks, its cool and I like it. Good for scenerio games and such.

I got it for the ease to aim and the "quiet" factor.