Overgassed? Pic Inside

[lungingturtle2]

Thanks for your reply hoot and wc, you guys are a wealth of knowledge and experience. I suspected that nothing is that easy. there's no such thing as a free lunch. mike.

[Hoot]

...snip...as gas is going into the tube, other gases, stored at the exit end, is being pushed out of the tube, at the same rate.

Yes, but it's a gas, not a non-compressable liquid. The impedance of a longer tube is higher than a shorter tube for the same gas pressure front. Increase the impedance and delay will occur, all else being kept the same. Whether it accomplishes what you need it to, would require real-time evaluation. I don't think we can dismiss it on face value though. Someone send gunnut one of those pigtail and one of those switchback tubes and lets see a pressure trace comparing them to a plain tube. IIRC, his traces capture the bolt cycle as well. Easy metric.

Hoot

[bushmeister]

[ http://www.reno4x4.com/forum/attachment.php?attachmentid=26885&d=1295285075 ]

I love the purple explanation!!

[45r]

Did some more shooting with my 450 and 36 grains lil gun ejects 3 oclock with very good accuracy using 225 ftx's.I'm real happy with my upper so far.Thinking about trying some 296,H-110 since I have a lot of it but the accuracy with lil gun is so good I could just stick with it.

[wildcatter]

...snip...as gas is going into the tube, other gases, stored at the exit end, is being pushed out of the tube, at the same rate.

Yes, but it's a gas, not a non-compressable liquid. The impedance of a longer tube is higher than a shorter tube for the same gas pressure front. Increase the impedance and delay will occur, all else being kept the same. Whether it accomplishes what you need it to, would require real-time evaluation. I don't think we can dismiss it on face value though. Someone send gunnut one of those pigtail and one of those switchback tubes and lets see a pressure trace comparing them to a plain tube. IIRC, his traces capture the bolt cycle as well. Easy metric.

Hoot

So True, but I didn't really want to get into such a detailed explanation, especially for real world results, that don't make any real difference. In other words, the gains of the pigtail, in regard to dwell time, is negligible, to non-existent. I can see it on my pressure trace, but holy-cow, it's measured in tenths of a nano-second or there-in about..

..t

[Hoot]

So True, but I didn't really want to get into such a detailed explanation, especially for real world results, that don't make any real difference. In other words, the gains of the pigtail, in regard to dwell time, is negligible, to non-existent. I can see it on my pressure trace, but holy-cow, it's measured in tenths of a nano-second or there-in about..

..t

Agreed WRT the pigtail type. Have you done any work with the one that folds back upon itself to actually add length to the path? I seem to recall seeing a picture of one somewhere. It's all mental chewing gum as the obvious choice is to relocate the port. The challenge is coming up with a near port gas block with a back entry hole for the far port and the ability to switch between the two, while cutting the other off. All that and not be too imposing. It can be done, but determining enough demand for one to justify the tooling becomes a bit of a challenge, for such an esoteric pursuit.

Hoot

[wildcatter]

So True, but I didn't really want to get into such a detailed explanation, especially for real world results, that don't make any real difference. In other words, the gains of the pigtail, in regard to dwell time, is negligible, to non-existent. I can see it on my pressure trace, but holy-cow, it's measured in tenths of a nano-second or there-in about..

..t

Agreed WRT the pigtail type. Have you done any work with the one that folds back upon itself to actually add length to the path? I seem to recall seeing a picture of one somewhere. It's all mental chewing gum as the obvious choice is to relocate the port. The challenge is coming up with a near port gas block with a back entry hole for the far port and the ability to switch between the two, while cutting the other off. All that and not be too imposing. It can be done, but determining enough demand for one to justify the tooling becomes a bit of a challenge, for such an esoteric pursuit.

Hoot

If you are talking about the one built by Tim LaFrance, then yes and it does work. Two things, he quit building them years ago (he still has some but they are about $200 per), and two, you got it!-Just relocate the gas block/port and be done with it, tons cheaper and far less complicated..

..t