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 O-ring sizes (for cartridges)

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smootik
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PostSubject: O-ring sizes (for cartridges)   Sat Apr 10, 2010 12:19 am

Guys,

Do you maybe know what are correct o-ring sizes for use in various modelgun cartridges?

I'm in particular after these for Hudson Skorpion, MGC 1911 .45 and Hudson Desert Eagle (same as MGC 1911 I believe).
Tried to measure ones for Skorpion - a tricky task, they get deformed while measuring.

Not sure what should I measure for ordering - thickness (for sure), but then it's inner or outer diameter?
Skorpion o-ring seems to be 2.4mm (internal), 1.2-1.4 (thick) and 5.1mm (external).
5.1mm is approximately 13/64"
2.4mm is approximately 3/32"
1.2mm is approximately 3/64"

Not sure how to map it all to size for order from o-ring/seal company. There seems to be a few standards for o-ring sizes: HNBR, SAE and Metric. Skorpion o-ring does not correspond to any standard size listed here:
http://www.allorings.com/size_cross_reference_framed.htm
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Cerwyn
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PostSubject: Re: O-ring sizes (for cartridges)   Sun Apr 11, 2010 10:55 am

This company in the UK were able to help me out

http://www.altecweb.com/home.asp?cat=RangeB05

I sent them a sample 7 and 5mm 0-ring with a descrption of the application they're used for.
They were able to measure them far easier than I could at home and sent me details of their recommended rings.
They'll happily sell small quantities to the public

The 7mm version is a fraction smaller on the o/d once placed onto the piston but they work fine during firing there's no appreciable difference that I can see.

Could be worth sending them samples if you can't get exact dimensions.

Also, there's a link on here to Lucifer's Blog pages... mentioned here http://mp40modelguns.forumotion.net/modelgun-videos-f2/marushin-mauser-m712-english-version-from-lucifer-t1497.htm If I remember correctly there are dimensions quoted with his drawings for the Skorpion 0-rings
Get onto Lucifer's youtube channel, follow link to his blog. I found Google translate useful

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smootik
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PostSubject: Re: O-ring sizes (for cartridges)   Sun Apr 11, 2010 11:58 am

Cerwyn, thank you for very useful information :-)

I did not think of providing a sample to a company, that should make things simpler!
I found a (almost) local company advertising a full range of o-rings, also sold in low quantities - will get in touch with them.

And watching Lucifer's work again in pretext of searching for information is just a pleasure ;-)
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PostSubject: Re: O-ring sizes (for cartridges)   Tue Apr 13, 2010 1:51 pm

http://lucifer7922.blog.so-net.ne.jp/2009-08-08

7mm cartridges seem to use Japanese JIS 2401 norm P-3 size o-ring, which is 2.80x1.90 (inner diameter x thickness).
The closest corresponding ISO size is 2.8x1.8, American size is 2.9x1.78 (11A039).

However for 5mm cartridges he seems to have chosen SS3.5 (?) 3.0x1.0 o-rings, and I'm not sure if this is for his own design, or original cartridge. There is such a size in NBR o-rings.

Further references:
Morisei Kako list of standards
Maryland Metrics list of standards
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PostSubject: "all" 7mm cartridges?   Tue May 18, 2010 8:47 am

smootik wrote:
http://lucifer7922.blog.so-net.ne.jp/2009-08-08

7mm cartridges seem to use Japanese JIS 2401 norm P-3 size o-ring, which is 2.80x1.90 (inner diameter x thickness).
The closest corresponding ISO size is 2.8x1.8, American size is 2.9x1.78 (11A039).

Is this size you've found true of all 7mm type cartridges regardless of manufacturer (ie: Marushin, MGC, et cetera)? And if so, were you ever able to find an online dealer/distributor that carried these O-rings? The reason I ask is because as I've been sitting here assembling some Cal.9mm cartridges for my Marushin Beretta m92FS (they came in a kit I recently acquired), I've discovered that I'm 2 o-rings short of completing all of them.
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PostSubject: Re: O-ring sizes (for cartridges)   Tue May 18, 2010 10:15 am

lowlight wrote:
Is this size you've found true of all 7mm type cartridges regardless of manufacturer (ie: Marushin, MGC, et cetera)?
Probably not. Size I provided was measured for MGC .45 cartridges (for Colt 1911).
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PostSubject: Re: O-ring sizes (for cartridges)   Wed May 19, 2010 6:43 am

smootik wrote:

Probably not. Size I provided was measured for MGC .45 cartridges (for Colt 1911).


I see, well, I went ahead and ordered them from Francky, as I didn't want to figure out where and how to find a maker/retailer of these little things. Based on my invoice, he charges about 23 cents (about 16p in the UK, I reckon) per O-ring; not too bad I suppose given the application.
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PostSubject: Re: O-ring sizes (for cartridges)   Wed May 19, 2010 9:41 am


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smootik
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PostSubject: Re: O-ring sizes (for cartridges)   Wed May 19, 2010 7:06 pm

Replacement (similar, not exactly the same size) O-rings that I found locally cost about 33 cents + shipping, so you got a better deal :-)
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PostSubject: Re: O-ring sizes (for cartridges)   Thu Oct 04, 2012 3:10 pm

Replacement 0-Rings would seem to be becoming harder to obtain from Japan these days and those that are, are expensive.

Accurately measuring 0-Rings at home proved impossible so as there's a HUGE range of sizes available from Automotive and Engineering sources so I gathered a range of samples to try. To order particular sizes, all rings I found are listed by Inside Diameter and Cross section of the material e.g.

MGC P220 cartridges intended for 7mm caps were used to test first in WaShan Full Metal Beretta M9 Dolphin pistol. With ALL sizes listed below, Volume of Noise from each cap was slightly less than that of standard MGC 0-Rings but were all perfectly acceptable.

Material = Nitrile Lubricated with Silicone Oil

Inside Dia: 3.17mm Cross Section: 1.78mm Good Blowback, Good Smoke, Good Sound

Inside Dia: 3.15mm Cross Section: 1.80mm Better Fit,Good Blowback & Smoke, Good Sound

Inside Dia: 3.40mm Cross Section: 1.90mm Tight Fit, Good Blowback, Less Smoke, Less Noise

Inside Dia: 3.00mm Cross Section: 2.00mm Tight Fit, Good Blowback, Less Smoke, Less Noise

Material = Rubber Lubricated with Silicone Oil

Inside Dia: 3.00mm Cross Section: 2.00mm Tight Fit, Good Blowback, Less Smoke, Less Noise

*** To Be Continued ***

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