Pig-tail gas tube?

[4thPointOfContact]

Am about to embark on a 10.5 inch SBR build and came across one at a gun show. So are they - -

Just another whiz-bang doodad that does nothing useful or,
solves a problem that I didn't know I had?

[Robb Jensen]

Save your money.

[Army Chief]

Rather than offer a technical opinion, let me just say this: Robb has forgotten more about the AR-15 than 98% of our membership -- myself included -- will ever know. I think you have your answer. =]

AC

[Joeywhat]

Curious to know why exactly they don't offer any sort of improvement. Not that I don't believe that they don't work, just curious to know the science behind it.

Is it a "if it ain't broke don't fix it" sort of thing, or does it actually hinder performance in some way?

[Megalomaniac]

As far as I understand it the pigtail tubes would do nothing, a longer length gas system works via the fact that further from the chamber = less port pressure, a pigtail tube is just making the same port pressure travel a longer distance, instead of bleeding pressure off from a lower pressure spot.

[markm]

As far as I understand it the pigtail tubes would do nothing, a longer length gas system works via the fact that further from the chamber = less port pressure, a pigtail tube is just making the same port pressure travel a longer distance, instead of bleeding pressure off from a lower pressure spot.

Exactly. No change in port pressure. And probably zero or negligible improvment from the additional tube length.

[Heavy Metal]

The PRI Fatboy is a better execution of this concept. The problem with the Pigtail is it has problems with the coil expanding when hot and affecting function.

[4thPointOfContact]

I had never seen a serious build using one, so I was pretty sure. Thanks for the confirmation. :jester:

[Eric D.]

Indeed. Since volume = piR^2 x L, increasing the radius of the tube increases the volume by a factor of 4, much more effective than lengthening it.

The problem is too much gas. The pigtail tubes attack the symptoms, not the root cause.


The PRI Fatboy is a better execution of this concept. The problem with the Pigtail is it has problems with the coil expanding when hot and affecting function.

[devinsdad]

Years ago, they were one of those "gotta have" things for your AR. Now, they are one of those "Holy crap, I can't believe I bought one of those" things. Pass on it.

[Mr blasty]

So does the PRI tube offer much for a carbine gas system then? How about on the SBR's as well?

[Robb Jensen]

So does the PRI tube offer much for a carbine gas system then? How about on the SBR's as well?

It works okay on VERY overgassed 14.5-16" CAR gas guns. I'm talking barrels with gas ports like .090" and larger. Even then you would be far better served with a new barrel with the correct sized port of .0625"