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All Springer/NP/PCP Air Gun Discussion General > PCP/CO2/HPA Air Gun Gates "The Darkside"

2260MB Tubes with Ground Finish - DO NOT USE FOR HPA

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Ribbonstone:
Well..."they" never intended them to be pressurized (with co2 or air)...so the work as intended. It's just individual's intentions/urges that are in conflict with that.

rsterne:
TKO22, thanks for the confirmation that the 2260MB tubes have changed and are now a thinner wall.... You say that the failure was the fill adapter blowing out the front at 4100-4600psi.... Were you using a Disco fill fitting, or something made from the CO2 cartridge retaining nut supplied with the 2260MB tube?.... Where was the O-ring, inboard or outboard of the threads?....

Your dimensions indicate that the ID of the new tube is 0.765", which is 0.020" larger than the ID of the Disco/Maximums/old 22XX tubes.... They were all 0.745" within a thou or two.... Do you know what threads are being used on the ID of the new 2260MB tube?.... Is it still 13/16"-28, or have they gone to something else?....

Regardless of the material, or the threads used.... the fact that the tube wall has been reduced from 0.065" to 0.049" will reduce the strength of the 2260MB tube by at least 25%.... If the material is of lower tensile strength, it could be a LOT less.... Anyone wanting to do an HPA conversion using one of the new, thinner wall tubes, must take great care....

Bob

Magnum Airpower:
 I have a 2260 MB tube in front of me right now along with Maximus, Marauder Pistol and Discovery tubes. All of them are exactly .0625" wall thickness with the threaded section of the tube varying from .049" - .051". (Updated in newer post below, measured an assortment of different tubes that measured .043" at the threaded section, those were Marauder Pistol and 1701P tubes. Both were exactly .875" OD with .0625" wall thickness at the back. Got the same tube OD and wall thickness for Discovery, 2240, 2250 and 2260 tubes with .045" to .051" at the threaded end.) The threaded section is always thinner than the rest so I'm not sure what part of the tubes you guys are getting your measurements from. The variances in OD and wall thickness TKO is reporting, I've never seen that in hundreds of tubes I've checked over the years. They are consistently .0875" OD and .0625" wall thickness. The 1020 DOM tubing Crosman buys for these tubes is extremely consistent in sizing, DOM in general is known for that level of precision.

 It's widely known I've had all of these tubes tested and know for sure they're the exact same .0625" wall thickness, 7/8" (.875") OD, 1020 DOM carbon steel tubing. Same steel alloy, same hardness with only slight manufacturing variances by Crosman. Even the tubes with stamped lettering will handle 3000 PSI safely with a failure pressure of over 10,000 PSI. All you need is to secure the valve correctly with three high-strength screws and make sure your fill adapter doesn't fit the tube threads sloppily. Unless Crosman just released a completely new version made form thinner tubing, which could be the case, it would still be safe to 2000 PSI so long as the fill adapter threads fit snug. I would have to test one to know the exact limit. I will check into that possibility and update this as soon as I know. Either way, the 2260MB tubes I've sold and the few I have here in my shop are all safe to 3000 PSI and have a wall thickness of .0625".

Bill, owner and manager of Magnum Airpower LLC   

rsterne:
The critical thickness, assuming the O-ring is inboard of the threads, is at that point, where the O-ring seals.... I don't have a 2260MB tube, but my bet is that Crosman have downgraded to a thinner wall tube.... even at 0.765" ID, it could still be threaded safely 13/16"-28.... However, the fill adapter and the O-ring groove in it would have to be different dimensions or it would not seal on the 0.020" larger ID....

Bob

avator:
Just as a disclaimer.... The tube in the build that I linked to is a true 2260 tube, not the 2260MB. I also only fill that gun to 2K.

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