|Originally Posted By tankdriver:
Originally Posted By BossMaverick:
Maybe I'm over thinking it, but please explain to me how the pigtail works so magically.
I think about it like a 25 foot air hose with a sudden 18,000+ PSI pressure spike at the supply end. The final PSI output pressure with a 35 foot hose isn't going to be noticeably different compared to a 25 foot hose. ETA: Please don't tell me that the extra 10 feet is going to delay 18,000+ PSI of air from getting to the end.
Gas port location and size is the biggest factor to gas tube pressures, not the length of the tube.
Click on this link, it goes over everything from earlier post.
Short of it, basally the longer tube slow down the initial plus as it has a longer distance to travel. Now this is not seconds, but mili-seconds. Which in a firearm can make a difference. I was a Boiler and A/C Operating Engineer for about 10 years, and in the old days you adjusted a A/C expansion coil(the cold one), not with an thermal, or pressure value, but with an expansion tube, or tubes. You adjusted the expansion of the gases by how long, or short you cut the tubes .
I had read that thread and there is this in it (which is how I feel):
From a fluid dynamic standpoint, the pigtail does nothing. The speed of the gas in relation to the speed of the projectile is a substantial multiple. For all practical purposes, once the bullet is past the gas hole, the pressure realized at the cylinder is instantaneous. We are talking gas expansion at probably well over 10,000fps (assuming no resistance). What matters is at what point the bullet passes the gas hole. Those few little inches of gas tube are irrelevant. It's pure snake oil.
I can see tube length making a difference in A/C systems. A longer tube would have more surface area which would allow the room temperature to have more of an effect on the temperature of the A/C gasses (like a radiator of sorts). Also, from my understanding of A/C systems, the cold side of the system is the low pressure side. Since we are talking thousands less PSI then a firearm, I can see a longer tube possibly having an effect of the system. I don't see a longer tube having an effect at firearm pressures.
I'm just not sold on the pigtail gas tube. Too bad there can't be high speed video like this to show if it actually makes a difference or not. The only way I could see the pigtail gas tube working is if it was more restrictive then a standard gas tube. If that was the case, a smaller gas port size would work just as well but possibly at the expense of reliability. IMHO, if timing is an issue, changing buffer weights would have more of an effect than a pigtail gas tube.
ETA: As far as recoil feeling compared to the other two pistol builds you shot, you mentioned that you had to drill your gas port hole one size larger to get the gun to work in the original thread. It could be that you still have a smaller gas port size then the other two AR pistols since we don't know the barrel brands.