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Barrel Porting


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#1 xedice

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Posted 25 March 2004 - 12:08 PM

Has anyone tested barrel porting and found a significant range/accuracy increase? I know the concept behind it, and that its used in paintball, but I am a bit sceptical about it in nerf. Just wanted to ask if anyone has tried it before I go dish out the money for more brass to test it.
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#2 david00790

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Posted 25 March 2004 - 01:19 PM

I don't know, but it sure looks cool :D
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#3 cxwq

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Posted 25 March 2004 - 02:08 PM

Tried it in two forms. One is slotted ports as evidenced on my homemade, the other is a reverse telescope that gets looser for the last couple inches of the barrel.

I don't have any firm results on the slotted ports because I didn't do significant testing before cutting them. Besides that, the homemade is too powerful to be very accurate.

I employed the reverse telescope method on my EaBs. They were originally 12" of 1/2" SCH80 and I changed them to 12" of 9/16" brass followed by 2" of 19/32" brass. The reverse telescoped brass is definitely more accurate. My EaBs are, by far, the most accurate guns I own. Even though they're only good for 70-80' flat, I can consistently hit people at 60-70' with a 5-10* barrel inclination.
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#4 Jangadance

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Posted 25 March 2004 - 06:30 PM

Reverse telescoping? Porting? Nesting? What?!

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I'm a bit confused with all these terms. I think porting has something to do with putting holes at the end of a barrel to diffuse the burst of air that is let out when the dart exits, right? As far as REVERSE telescoping goes, I have no clue. From cxwq's description it sounds like telescoping with a longer first piece of brass than usual. For that matter, what's the difference between telescoping and nesting brass? A telescope can have the pieces overlap, but it extends so that the pieces fit almost end to end for material efficiency. Anyways, just some clarification would be keen.

Edited by Jangadance, 25 March 2004 - 06:34 PM.

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#5 cxwq

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Posted 25 March 2004 - 11:27 PM

Porting, as you guessed, involves vents in the end of the barrel, designed to release excess pressure so that it doesn't perturb the dart flight as much as it otherwise would.

I cut slotted porting in my homemade as shown here

Posted Image


Reverse telescoped is bad terminology, which I'm good at generating.

Telescoped and nested both refer to a barrel that gets larger in diameter as the dart travels down it. What I'm talking about is essentially the same thing but with a different goal than 'traditional' nesting. Rather than holding the dart tightly, then allowing it to move more freely, my EaB barrels allow the dart to move freely, then during the last two inches, increase in diameter to allow air to begin flowing around the dart. Hopefully this reduces the turbulence of early flight, and my rather subjective accuracy testing seems to suggest success.
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#6 Jangadance

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Posted 26 March 2004 - 03:17 AM

... originally 12" of 1/2" SCH80 and I changed them to 12" of 9/16" brass followed by 2" of 19/32" brass.

I've been thinking of brassing at least one of my EaBs, and possibly using 1/2" Sch. 80 PVC on the other. What do you feel 1/2" Sch. 80 PVC's ID is equal to in terms of K&S brand brass? Also, would you recommend this system of porting without holes over a more standard telescoping brass job that AlextheBeast claimed helped him achieve 120 feet "flat" with?

About the "reverse telescoping" name... Once I started typing I began to see where you were coming from: the brass in your EaB telescopes with a long brass tube that goes into a larger ID short brass tube. This is the reverse of normal telescoping barrels, in which there is a short piece of the thinner ID barrel that connects to a longer piece of the wider fit barrel. The "reversed" brass barrel is rather, a delayed graduation of the brass pieces. Which in this case is helpful in diffusing the turbulence caused by the large volume tank the EaB features.

Lastly, I don't mean to go off topic some more, but how long of darts do you use in your EaB, cx: and are they any different than your standard darts for a blaster like the AT3k or MS?

Edited by Jangadance, 26 March 2004 - 03:19 AM.

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#7 cxwq

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Posted 26 March 2004 - 03:13 PM

I've been thinking of brassing at least one of my EaBs, and possibly using 1/2" Sch. 80 PVC on the other.  What do you feel 1/2" Sch. 80 PVC's ID is equal to in terms of K&S brand brass?  Also, would you recommend this system of porting without holes over a more standard telescoping brass job that AlextheBeast claimed helped him achieve 120 feet "flat" with?

[..snip..]

Lastly, I don't mean to go off topic some more, but how long of darts do you use in your EaB, cx: and are they any different than your standard darts for a blaster like the AT3k or MS?

If I recall correctly, 1/2" SCH80 is somewhere between 17/32" and 9/16" ID which would put it between 9/16" and 19/32" (OD) K&S brass.

For the EaB you want at least 12" of barrel. If you're willing to use a ramrod and kill your ROF, do a standard telescoped brass barrel like Alex did. Though he hasn't responded (in the thread you linked) to my questions, I'm sure you could get 100' flat out of that mod. If you want a higher ROF, go with either 14" of SCH80 or the 12"+2" brass I described above. Which you choose will largely depend on your FBR. You want a good sliding fit with very little resistance, but not so loose that there's a visible gap between dart and barrel. SCH80 was slightly too big for my darts so I got better performance with brass.

I haven't measured my EaBs since brassing them in this fashion, but I'd guestimate around 80' flat and hella accurate with high ROF. To load, I drop a dart in, point up, and cock. Gravity plus the plunger retreating are sufficient to get the dart all the way down the 14" barrel.

I use the same darts with all my guns except my homemade. They are 1/4" steel slingshot ammo weighted 2.25" micro stefans. This dart works well with any mid to high power gun. I could get more range out of my sidearms with slightly lighter darts but it's only a small compromise.
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