Installing a 5/16" OD Transfer Port in a Disco
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Installing a 5/16" OD Transfer Port in a Disco
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Topic: Installing a 5/16" OD Transfer Port in a Disco (Read 7643 times))
HillGSA
Sharp Shooter
Posts: 874
yes
Real Name: Tim
Re: Installing a 5/16" OD Transfer Port in a Disco
«
Reply #20 on:
January 21, 2015, 07:27:11 PM »
Thanks for sharing
I tried using the more rigid materials too, but I could not get them to seal properly. After testing, it seems to me that a compressible material of some sort ( of at least .030 or more = see pic ), is need between the transfer port, and valve body ( exhaust port ) to seal properly ( no leaks during the shot cycle ). Or is a "certain" amount of leakage "acceptable" ?
Is this technique transferable from rifle to rifle, or specific to each application ?
Does
it pass the tissue test - no air leaks ( see pic )
Thank you in advance
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rsterne
Member 2000+fps Club
Bob and Lloyd
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Real Name: Bob
Re: Installing a 5/16" OD Transfer Port in a Disco
«
Reply #21 on:
January 21, 2015, 08:46:43 PM »
A Teflon port, cut square on both ends and about 0.010" longer than the space it fits into, works great, and can pass the tissue test.... If you made it 0.030" longer than the space, you would not be able to screw the breech down with that tiny 4-48 screw in the Disco.... I find that Delrin can be made to work, if you get the perfect length, but that is the problem.... any of these plastic tubing systems are a "cut and fit" deal, specific to the way you machine the valve and the barrel, as the depth of those flats, plus the thickness of the breech, governs the space available.... but then you know that.... Once you find the right length, you can make a stack of them, and they will all fit and seal.... If you machine a bunch of valves and barrels all the same (and use the same thickness breech), then they can be mass produced....
That wasn't really the point of this thread, however.... It was a "how-to" for the home modder who doesn't have access to a mill, and doesn't want to be limited to the 1/4" OD transfer port in a Disco.... If you have the room, and the equipment to make it, a metal transfer port with O-rings both ends is very tolerant of, well, tolerances, but with the 7/16" barrel OD on a Disco, that limits you to a 5/16" OD O-ring, which is usually 3/16" ID.... The Teflon sleeve works well up to 7/32", and hence can handle a .30 cal with ease, and even a .35 cal if you don't need over 200 FPE....
Bob
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Installing a 5/16" OD Transfer Port in a Disco