 |  | | | |  | |  |  | Shortened Disco Air Tubes For Crosman 22XX HPA conversion |  | |  |  | |
 Posted: Sat Jul 30, 2011 9:25 pm |
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| Mark5043 |
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| Joined: 12 Apr 2009 |
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| Anybody know who offers these?I'm looking for one that's 16" in length.I know Don Cothran can machine one from stainless steel. I'm just looking for someone who offers stock Disco tubes of various lengths,and am having trouble sourcing that....thanks. |
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| Posted: Sat Jul 30, 2011 9:50 pm |
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| rsterne |
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| Joined: 15 Jan 2008 |
| Posts: 2998 |
| Location: Coalmont, BC |
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B&A will cut Disco tubes to whatever length you want and then rethread for the fill fitting....
Bob |
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Sun Jul 31, 2011 11:41 am |
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| Mark5043 |
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| Joined: 12 Apr 2009 |
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Thanks Bob.I've contacted both B&A,and Don Cothran to get some prices.  |
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| Posted: Sat Aug 06, 2011 10:00 am |
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| Mark5043 |
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| Joined: 12 Apr 2009 |
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| No word from Don yet through e-mail...I'll give him a call.B&A got right back to me though. $61.00 shipped for a custom cut tube. |
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| Posted: Tue Aug 09, 2011 9:19 pm |
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| 1377x |
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| Joined: 03 Mar 2010 |
| Posts: 38 |
| Location: upper midwest usa |
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| Mark5043 wrote: |
| No word from Don yet through e-mail...I'll give him a call.B&A got right back to me though. $61.00 shipped for a custom cut tube. |
not bad
i recently had one done it cost me $50usd including the tube
the tube's id is smaller than the fill adapter when it gets cut,so it has to be honed to get it threaded to fit
worth it if you want a carbine ,imo |
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| Posted: Tue Aug 09, 2011 11:20 pm |
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| Mark5043 |
| Silver Status Member |
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| Joined: 12 Apr 2009 |
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| yeah that price seems pretty fair.I still haven't made up my mind though.Still no word from Don in regards to my Email.I've heard his pipes are top notch,but not answering an Email makes a guy wonder...Maybe he's just really busy.Time to pick up the phone I guess.By the way how long is your tube,and how many full power shots per fill may I ask?I'm hoping for 12-15,with my set up,as that would be perfect.This gun is going to be a hunter,not a plinker. |
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| Posted: Wed Aug 10, 2011 12:13 pm |
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| rsterne |
| Moderator |
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| Joined: 15 Jan 2008 |
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| Location: Coalmont, BC |
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I have a 2260 tube on my PCP Carbine and I get 15-16 good shots at 20 FPE (18.1 gr. @ 700 fps).... 2000 psi fill and 1100 psi refill.... The tube is just shy of the end of the barrel, in fact the fill fitting is slightly beyond it without the muzzle end (only adds 1/4").... The tube is 16.625" long, but I have an extended front end on the valve to place the O-rings in front of the roll-stamped area for safety.... and that reduces the inside length and volume.... With a Disco tube you wouldn't have to do that for safety, but you will have to cover the gauge port which effectively will create the same situation....
Figure about 1.25 FPE/CI of air to get a rough estimate of the volume you require.... If you want 15 shots at 20 FPE that's 300 FPE.... 300/1.25 = 240 CI of air at 1 Bar.... A 900 psi pressure drop is 62 Bar.... 240/62 = 3.87 CI volume for the reservoir.... Since the tube is 0.745" ID that's 0.44 sq.in.... 3.87/0.44 = 8.8" of length from the front of the valve to the back of the fill fitting.... My tube is a bit shorter than that, but my efficiency was slightly higher.... Anyway, you get the idea....
Bob |
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_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Wed Aug 10, 2011 2:38 pm |
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| Mark5043 |
| Silver Status Member |
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| Joined: 12 Apr 2009 |
| Posts: 1379 |
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Thanks for the information.It helps a-lot... 
I can see I'm on the right track...but of course I have a few more questions.
I haven't decided whether or not to install a gauge yet.I'm assuming if I chose not to I could just use a brass or steel plug of the proper thread size,with the threads wrapped in Teflon tape to help seal it?Would that hold up under pressure?
If I chose to use a gauge could I remove the extension that is between the gauge,and the tube,and just screw the gauge directly into the tube?My objective here would be to have the gauge as close to flush with the tube as possible.
Not done yet...a couple more... 
It looks like you have a 12" barrel on your rig?
I ask because I'll be running a 14.5",and just trying to get a feel for
what kind of numbers to expect.
I'll be running a stock disco valve with hammer spring,and a power adjuster.This is the rig I'll be doing the conversion on...
....and finally what breech is that?...I'm looking to go repeater as well,and am looking hard at the Cobra venom,as it takes the 10 round Marauder rifle mag... |
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| Posted: Wed Aug 10, 2011 9:09 pm |
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| rsterne |
| Moderator |
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| Joined: 15 Jan 2008 |
| Posts: 2998 |
| Location: Coalmont, BC |
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The gauge mounting block in the Disco is NOT 1/8" NPT thread, it is a straight thread and the extension is sealed with an O-ring.... Therefore you cannot just screw the gauge directly into the gauge mounting block.... nor can you use a pipe plug.... There are three solutions, either you can make a new block with 1/8" NPT threads in the side for a gauge.... or no hole, just the two O-rings.... OR you can make an extended front end on the valve like the one's Joe (Muzzle Mack) sold.... maybe he still has some?.... Then you don't have to run a gauge at all.... the O-ring is ahead of the gauge hole in the Disco tube....
The barrel on my carbine is a stock 14.5" Crosman.... I restricted the transfer port to 0.125" instead of the stock 0.140" to get more shots and a flatter shot string.... Stock Disco valve, hammer, and spring, with RVA.... With the same power and a stock TP the best I could do was 14 shots instead of 16 and greater shot-to-shot variation.... The smaller TP made a difference and just needed a bit more hammer spring preload to get the velocity back.... Added benefit was better efficiency as well (2 extra shots!)....
Bob |
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_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Thu Aug 11, 2011 2:42 pm |
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| Mark5043 |
| Silver Status Member |
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| Joined: 12 Apr 2009 |
| Posts: 1379 |
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Okay thanks Bob.I'll add this info to my build notes for sure.  |
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