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:
<font face="Verdana, Helvetica, sans-serif" size="2">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. </font>...
one might conclude that if you keep porting past the 8-10 inch mark, you can have as many holes in the barrel as you want and it will not negatively affect the ball?

And any porting done before that is simply more of a hindrance to the ball velocity unless you increase the amount of gas used (and the speed at which it uses it)? Sounds right to me. http://www.automags.org/ubb/smile.gif

So, long barrels with porting VS short barrels with NO porting could very well BOTH be a hindrance to ball speed and the efficiency of your marker.

Example:
A 6 inch non-ported barrel does not use the full 8-10 inches of useful (or effective) ball acceleration distance. This would make it less efficient.

A 14 inch barrel with 7 inches of porting will be the same thing... being that the effective distance of the barrel is still only 7 inches.

However a non-ported barrel of 9 inches is pretty efficient.

And a 14 inch barrel with 4 inches of porting is ALSO pretty efficient.

And these two barrels would require the SAME amount of air pressure to propel the ball the SAME distance. Why? Because they BOTH have the same "effective" barrel length.

So, the argument of which is better (or more efficient), is a bit irrelevant if left at that. There are other factors to look at. So your answer would be correct if you argued it either way... again, depending on the actual barrels. http://www.automags.org/ubb/wink.gif

And might I throw another twist to this argument? If any porting after 8-10 inches is pretty much useless as a propulsion factor, and the gas pressure is too low to actually assist the ball in any way... why would you even need the porting?

To create a spin? No, remember that the actual gas pressure is too low to push the ball, so why would you think it would be high enough to spin it? My theory.....

The porting is done to RELIEVE back pressure caused by the ball traveling at a speed greater than the gas now pushing it.... the barrel would in effect then cause a slight suction on the ball.. slowing it down? hmmm This would indicate that the porting is to let air IN and not the other way around. If you let air in after the ball, you effectively relieve the vacuum caused by the ball without reducing the overall ball speed.

If this is the case, it would make sense that any barrel over 8-10 inches SHOULD have porting.. or else the barrel itself would be a hindrance to the efficiency of the marker.

And then wouldn't straight porting work just as well? Sure, but then you can't sell the idea that the porting spins the ball. http://www.automags.org/ubb/wink.gif And the spiral porting looks so cool. http://www.automags.org/ubb/wink.gif

Which brings up the point... if this is also the case, why even have barrels that long? http://www.automags.org/ubb/wink.gif Looks?

I hope someone more "techie" can help clear this up. http://www.automags.org/ubb/smile.gif

Just my thoughts.

------------------
“The richest man is not the one who has the most, but the one who needs the least.”


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

[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]

Good points, but may I suggest this?

If you have the correct barrel, and the correct pressure, you will be more efficient... thus getting more shots out of the same canister WITH the desired accuracy.

It is like tuning an engine. There are so many variables, but when they are ALL correct, the engine will give you MORE power for the same amount of fuel.. thus directly causing an efficiency issue.

You can take a poorly tuned car, give it more gas, and it will run faster... but that is really not what most of us want. We want MORE power with LESS gas. And I think this is at the heart of the question... what will make me shoot BETTER, with less gas. It allows you to get more accurate shots per canister.

I think we will all agree that it is not just a matter of how many balls you can shoot... if that was the case you could set your marker to such a low setting that you would only shoot the ball 3 feet. http://www.automags.org/ubb/wink.gif

And I think we would also agree that this would not be "efficient" use of your resources. Even if you could accurately determine where the balls will land at that 3 foot distance. http://www.automags.org/ubb/smile.gif

Like I said, I think the question was a bit too simplified to begin with, to get a perfect and absolute answer. http://www.automags.org/ubb/smile.gif

(oh, and I think I should clarify.... I was not saying that porting is not a factor. I was suggesting that it would only be a negative factor in respect to needing more gas to create the same effect, IF the porting was done before the 8-10 inch point. Anything after that should not be an issue as it pertains to needing more gas, since that is now past the effective acceleration point anyway.)

------------------
“The richest man is not the one who has the most, but the one who needs the least.”

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

[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!! http://www.automags.org/ubb/wink.gif

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]

LOL Very true!

How does it all work? Heck if you use a good enough marketing team, you can say it works any way you WANT it to.. and people will fight to the death trying to prove your points.

Look at all the fights over "what marker shoots faster". etc..

Perception is a powerful thing. http://www.automags.org/ubb/wink.gif

------------------
“The richest man is not the one who has the most, but the one who needs the least.”

[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.