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Air Gun Home Forum Index » Rifles » More on converting a discovery Goto page Previous  1, 2, 3  Next
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PostPosted: Sat Jul 18, 2009 10:04 pm Reply with quote
Jaxom
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Ya know, you guys are starting to make me wonder if I should go with a disco valve for my kt project. But with only 14" long barrel, what gains would I really get from it.

Can't wait to see the numbers you get as a comparison, bob. I'm curious though, is there anyway using the numbers you've already gatherd you could slew those out to see what I can approximatly be looking at in .25 calber using pellets that are say 25gr to 40gr? Later on, once I get more gear such as chrono, we can then compare and see how well those projections came out.

Still no suggestions on breech options, eh? <sigh>

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PostPosted: Sat Jul 18, 2009 10:42 pm Reply with quote
rsterne
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The Disco valve is the same inside as a 22XX valve.... the only difference is the front end which seals into the main tube with two O-rings.... and it has three 8-32 mounting holes.... Oh, and it has an O-ring seal on the valve stem and a molded over valve poppet instead of the brass with the soft insert.... What I'm trying to say is that performance-wise there should be no difference between a Disco Valve and a 22XX Valve....

The B&A Boss Max-Flow is larger inside and has a funnel shaped front end.... both of which mods you can do to a Disco valve.... Since it's designed for CO2, you have to mount it securely in the tube if you are using HPA.... and according to Joe the valve poppet material isn't great on HPA.... If the B&A Valve had a poppet and mounting holes like a Disco, it should be great, especially on a .25 cal....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
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.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26
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PostPosted: Sun Jul 19, 2009 9:02 pm Reply with quote
Jaxom
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So, if I understand this right, I'd take a boss max flow, swap out a mountain air valve stem and then use the disco valve top end to make for a complete "enchanced" valve system?

Still researching breeches. Wrote Robert over at RJ machine to see if he'd be willing to make me a long riser breech and extended bolt that'll fit a .25 cal lothar barrel. He turns me down, this project is done for me...

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PostPosted: Sun Jul 19, 2009 9:14 pm Reply with quote
rsterne
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If by a Disco "top end" you mean the part with the exhaust port.... doing that would lose the advantage of the Max-Flow being larger inside with an angled transfer port.... I don't see the point.... other than to get the O-ring stem seal....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26
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PostPosted: Sun Jul 19, 2009 9:21 pm Reply with quote
Jaxom
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Guess I was wrong then. What do you mean by popette?

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PostPosted: Sun Jul 19, 2009 9:55 pm Reply with quote
rsterne
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By poppet, I mean the actual part of the valve that moves when struck by the hammer.... a steel stem with that part that seals the valve attached....

In a 22XX, the head of the poppet is brass and contains a relatively soft sealing surface.... the Boss Max-Flow is the same.... It is designed for CO2 pressures....

In a Disco valve, the head of the steel stem is flattened and larger, and there is a "molded over" white plastic part that does the sealing.... It is a pretty hard material, and works well with HPA.... The stem is sealed with an O-ring....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26
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PostPosted: Sun Jul 19, 2009 10:14 pm Reply with quote
Jaxom
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Sounds like using a mountain air delrin valve stem would fix that issue then, right?

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PostPosted: Mon Jul 20, 2009 9:50 am Reply with quote
rsterne
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That's what Joe says.... never tried one.... Mr. Green

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26
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PostPosted: Mon Jul 20, 2009 5:45 pm Reply with quote
Jaxom
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Good to know, I was going to use a MA valve stem for my kt project.

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PostPosted: Tue Jul 21, 2009 2:42 pm Reply with quote
Jaxom
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Heard back from Robert at RJ Machine. He's back logged and cannot do the breech for me. Anybody know of any other companies doing after market breeches?

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PostPosted: Thu Jul 23, 2009 7:11 pm Reply with quote
Jaxom
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Wish I had a Discovery in front of me, so I wouldn't have to bug you all with boring questions.

If I can't buy a custom breech that can accept a .25 caliber barrel, can I modify the barrel or the .22 caliber breech to fit a .25 barrel?

Lothar makes two different size .25 caliber barrels. One is .591" and the other is .630".

First off, what's the I.D. of the barrel sleeve and what material is it made of? Also it would be handy to know what the O.D. of a stock .22 caliber barrel is as well.

What I'm starting to think I may have to do this modification over time, just like I've been working on my kt project now since February. I can buy a discovery, do most of the mods, and then once I can afford a lathe, I can get a replacement breech and perhaps experiment with making the .25 change then. In the meantime I can do all the other mods and tunes so I can use heavier .22 pellets until I convert over to .25 caliber.

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PostPosted: Thu Jul 23, 2009 8:41 pm Reply with quote
rsterne
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The Disco barrel is from a 2260 (or 1760).... and the OD is 7/16" (0.437").... Wink

The Disco barrel sleeve only serves to mount the rear sight, as far as I can tell.... however, the Disco breech is counterbored for it to slide inside (can't remember how far, maybe 1/2"?).... The barrel sleeve is 7/16" ID and 9/16" (0.563") OD.... HOWEVER, the bottom of it is machined down to only maybe 0.15" thick to clear the gas tube.... Rolling Eyes

If there was more clearance between the barrel and the gas tube, all you would have to do to fit a LW barrel would be to turn down the outside to fit in the Disco breech and drill the transfer port in the right place.... and then figure out what to do for a bolt and seal.... However, even a 1/2" OD barrel would touch the gas tube, so to fit a LW barrel you will need a riser breech.... Wish that wasn't the case, as I'd love to try a .25 cal Disco as well.... Twisted Evil

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26
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PostPosted: Thu Jul 23, 2009 9:33 pm Reply with quote
rsterne
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I understand you can buy a .25 cal conversion kit from Mountain Air:

http://airgunhome.com/agforum/posting.php?mode=reply&t=3615

about two-thirds of the way down the page.... no photo.... $165.00 for a barrel and bolt to fit your breech....

I note he offers the Disco in .25 cal ready to go as well.... Shocked

http://www.mountainaircustomairguns.com/model_15.htm

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal:
.177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26
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PostPosted: Thu Jul 23, 2009 10:18 pm Reply with quote
sniper
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what numbers would a .25 disco hit????

hmmmm. marauder upgrade? Shocked

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PostPosted: Thu Jul 23, 2009 10:52 pm Reply with quote
Jaxom
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Thank you bob! It never clicked with me! I've been on that page a dozen or more times looking at parts for my kt project! Just gotta hope when the time comes he has them!

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