GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: rsterne on March 08, 2019, 12:54:59 PM
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I just found this warning from TKO22.... I have no first hand knowledge of this, but PLEASE check this out if you are considering using HPA on a gun equipped with a 2260MB tube.... Even bulk filling with CO2 would be questionable, as the safety margin if the gun is left inside a hot car would be less than 3:1.... CO2 can reach 1900 psi at 120*F....
TKO22 SAYS:
The Crosman 2260 air tube has recently been changed by Crosman.
The new tubes are marked: "2260MB".
These ARE NOT THE same as the old 2260 tubes. They are 0.049 wall and machine very differently than the old "2260" tubes (0.065 wall). The 2260MB tubes also have a hard step at the front threaded end that will make it very difficult to get it to seal with a Discovery fill adapter. The 2260 tubes are chamfered for a smooth squeeze on the adapter o-rings.
I have hydro'd a couple of the newer 2260MB tubes, and they failed at ~4100-4600 psi. In each case, the fill adapter blew out the front.
I have assembled about 50 PCP pistols and carbines over the course of 5-6 years, using the 2260 tubes and no failures reported. I wouldn't use a 2260MB tube except for a Co2 cartridge gun.
If this is in fact true, this thread should be made a sticky, IMO.... Stay Safe !!!!
NOTE: This appears to have been caused by Crosman grinding down the OD excessively on some 2260MB tubes during the finishing process.... Do NOT use these tubes with a ground exterior finish for either bulk fill CO2 or an HPA conversion, as the wall thickness may be uneven and thin enough in places to be unsafe at increased pressures.... See Reply #45 on Page 3 for details....
Note, these tubes are fine for use with 12 gr. CO2 cartridges, as intended, because the tube is not under pressure....
Bob
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I sure hate that I just last week bought a 2260MB Sheridan tube from Magnum Airpower {Bill} set up for HPA and have all the parts ordered for complete HPA gun. I will contact Bill and see what he says.
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I just got off the phone with Bill - Magnum Airpower he said 2260MB tube same material and thickness as Discovery , 1720T etc. and that he has tested them to be sure . Sounds good to me .
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Don't have any new Crsoman tubes...but if the numbers are right, then I'd certainly pass on PCP use.
Don't really have a horse in this race, no Crosman tubes under pressure (air or bulk fillco2) so no personal envolvment pro or con.
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I just found this warning from TKO22.... I have no first hand knowledge of this, but PLEASE check this out if you are considering using HPA on a gun equipped with a 2260MB tube.... Even bulk filling with CO2 would be questionable, as the safety margin if the gun is left inside a hot car would be less than 3:1.... CO2 can reach 1900 psi at 120*F....
TKO22 SAYS:
The Crosman 2260 air tube has recently been changed by Crosman.
The new tubes are marked: "2260MB".
These ARE NOT THE same as the old 2260 tubes. They are 0.049 wall and machine very differently than the old "2260" tubes (0.065 wall). The 2260MB tubes also have a hard step at the front threaded end that will make it very difficult to get it to seal with a Discovery fill adapter. The 2260 tubes are chamfered for a smooth squeeze on the adapter o-rings.
I have hydro'd a couple of the newer 2260MB tubes, and they failed at ~4100-4600 psi. In each case, the fill adapter blew out the front.
I have assembled about 50 PCP pistols and carbines over the course of 5-6 years, using the 2260 tubes and no failures reported. I wouldn't use a 2260MB tube except for a Co2 cartridge gun.
If this is in fact true, this thread should be made a sticky, IMO.... Stay Safe !!!!
Bob
I have three tubes in front of me:
A 2260MB, a Discovery and a Maximus tube.
The 2260MB tube wall is .049. OD: .863
The Discovery tube wall is .063. OD: .875
The Maximus tube wall is .065. OD: 874
Average of 3 measurements each.
Probably the same material as they machine identically, but not the same dimensions.
It would be a good idea to measure and verify dimensions with any 2260MB tubes you are considering for a PCP build.
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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.
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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
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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
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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
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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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Sorry for the confusion, I thought I had posted the link in this thread.... here is the link to the build.
https://www.gatewaytoairguns.org/GTA/index.php?topic=152894.msg155681743#msg155681743 (https://www.gatewaytoairguns.org/GTA/index.php?topic=152894.msg155681743#msg155681743)
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The description of a hard transition the o-ring doesn't pass over easily, this would only exist if the tube got thicker than the thread major. The tube would have to be the same outer diameter, not smaller, for there to be threads large enough to fit a fill adapter or piercing cap. So the wall thickness at the threaded section to the thread major would have to be around .049" for the adapter to fit a hold over 4000 PSI before blowing out. That means the inner diameter would have to be larger to have a .049" wall in the non-threaded tube section. That would eliminate the hard transition some tubes have. I plan to order a 2260 tube Monday but will be out of state for two weeks before I will be back to check it out. In the meantime some photos with caliper readings of the back of that tube would be helpful. Also the serial number of the tube so the date it was made can be determined. Most of the tubes I've come across were made in 2015 - 2017 and those, like I said earlier were .0625" wall thickness. My custom adapters have the threads machined over-sized to fit Crosman tubes tighter. As far as I know I'm the only one who does this. I'm aware of fill adapters made by others that blow out at much lower pressures but dare not mention their names here to avoid all the drama that would result. Discovery adapters generally fit well and have stronger threads than the Marauder Pistol version. I usually suggest those as a cheaper option.
Bill
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I don't understand what you mean that the tube would have to be larger OD, not smaller to fit the fill adapter.... I looked up the thread dimensions for 13/16"-28, and the minimum minor diameter of the female thread is 0.774".... A standard Disco/22XX tube is nominally 0.875" OD x 0.065" wall, which means it is 0.745" ID, and has to be bored out nearly 0.030" to be threaded.... The dimensions that TKO22 has from his 2260MB tube is 0.863"OD x 0.049" wall, which is 0.765" ID.... That means it still needs to be bored out to be threaded, just not as much.... If the tube was 0.875" OD x 0.049" wall, the ID would be 0.777", which means it would not have to be bored out at all to be threaded, but would still be within the tolerance for 13/16"-28 threads, which can have a maximum minor diameter as large as 0.780" for class 3A threads, or 0.782" for class 2A threads....
I'm not arguing that your 2260MB tubes aren't the same as a Disco/old 22XX/Maximus tube, I'm confident they are, you are a reputable machinist.... I have several 2260 tubes here, and they are all the same 0.745" ID and 0.065" wall thickness as a Disco tube.... What concerns me is that we have a report that there is a new, thinner 2260MB tube, with a 0.049" wall, that has had the fill adapter blow out at 4100-4600 psi.... I have no reason to disbelieve that such a tube exists, and assuming it does indeed exist, then we need to investigate it, and make sure that nobody gets hurt because they believe that all 2260 tubes are created equal....
I will make an unfounded guess here that if the new tube is indeed 0.020" larger ID, and if somebody puts an existing Disco fill fitting into it, (which is about 0.740" OD at the O-ring) then the O-ring (under 4000+ psi pressure) extrudes into the gap, leaks, and the threads become pressurized.... Since the OD of the threads is 0.813", if the OD of the tube is indeed 0.863", then the remaining wall thickness of the threaded portion is only 0.025".... That would yield at 4100 psi, the tube would stretch in diameter, and the fill fitting would blast out the end.... In other words, there would be two contributing factors combining to cause the failure at such low pressure.... The tube being a thinner wall, creates a larger gap, which allows the O-ring to fail, and then when the threaded area is pressurized, the tube expands and the plug blows out the end.... It would be a perfectly logical fit for the failure mentioned....
Please, let's just combine our efforts to insure that if this is happening, nobody gets hurt because of it....
Bob
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Thanks for the post and information on this Bob. Are the part numbers for the 2260 "WC" tube and the 2260MB tube both 2260-004? I just purchased a 2260-004 two days ago before finding this discussion.
If they are using a thinner walls for the 2260 the 2240 and 2250 tubes should be checked as well before HPA use.
Speculation: as a cost savings measure they may have calculated it driving production sales vs DIY. A $9.00 pressure tube helps keep project costs lower than some production guns.
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I have no idea if they changed the part numbers.... What is the wall thickness on your tube, measured at the back?.... ID and OD?....
Bob
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I too ordered a 2260 tube on Friday 3/8/19.
I had intended for it to eventually be a Bulk feed project.
You can sure bet I will check the stamping, serial number, and get out the calipers and be measuring it when it arrives this week.
I'll report here when it's in hand.
What I find curious is I have not seen a 2260MB (Metal Breech) on Crosman's website and I have been researching them for a couple years. The only one I have seen is the plastic breech Heritage 2260 (Model: 2260WC).
I was starting to believe that PA / AGD / AV were putting the 2240SBPK metal breech kits on the Heritage in house.
Why would Crosman change all tooling over to designate a model "2260MB" they do not sell?
I also noticed TKO mentioned this...
The 2260MB tubes also have a hard step at the front threaded end that will make it very difficult to get it to seal with a Discovery fill adapter. The 2260 tubes are chamfered for a smooth squeeze on the adapter o-rings.
Is that chamfer the reason the wall is measuring thinner at the front of the tube? I presume it would be a "lead-in" for the o-ring to be inserted without cutting it on a sharp edge.
...But then what do you mean by the "hard step"? Is there a shoulder on the ID internal of the threads?
Bob, Is that the reason you wanted measurements taken at the rear?
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Why would Crosman change all tooling over to designate a model "2260MB" they do not sell?
If I understand correctly it eliminates one step in the Machining process which is boring the ID out for the minor diameter of the 13/16-28 screw thread on the front cap. So instead of having to bore that out to .049 wall thickness they start at .049.
Can anyone confirm that these 2260MB tubes are laser etched or are they also stamped like the previous .065 run?
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Why would Crosman change all tooling over to designate a model "2260MB" they do not sell?
If I understand correctly it eliminates one step in the Machining process which is boring the ID out for the minor diameter of the 13/16-28 screw thread on the front cap. So instead of having to bore that out to .049 wall thickness they start at .049.
Can anyone confirm that these 2260MB tubes are laser etched or are they also stamped like the previous .065 run?
I first reported my findings on the 3 2260MB tubes I received from Crosman about 2 years ago.
I recall it was on the old Crosman Green Forum.
The 3 "MB" tubes I received were roll stamped.
I posted some pictures on an earlier GTA thread, but we have since updated our servers, and those photo links probably are orphaned.
I'm traveling today and back to the shop sometime tomorrow after noonish. I'll dig hem up and re-make the directory structure on our server so the photos will display.
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It would indeed make economic sense for Crosman to use 0.049" wall tubing that was 0.875" OD, because they would not have to bore it out for the 13/16"-28 threads, they could just run the tap in.... Cheaper tubing and one less step in manufacturing, plus CO2 cartridges with paper labels would no longer get stuck inside the tube.... Win, win, win for Crosman…. ::)
Not only that, the Disco/Maximus valve would no longer fit properly, although they might have to make a larger OD hammer.... or maybe not, just let it rattle around?....
Bob
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In response to Bob, what I meant was the ID would have to be smaller than a wall thickness of .049" would allow in order to have a hard transition to the unthreaded section of tube. In other words the ID would be larger with a .049" wall, large enough the o-rings would pass through the transition easily.
After the most recent update by TKO I'm even more suspicious of the thin-wall theory. I sincerely mean no disrespect, it's just that all of the 2260 MB tubes I've been working with are from that two year period he states his measurements are from. All my tubes were .0625" wall thickness with the threaded section dropping to .049" from the OD to the thread major. All of them fit Discovery and my custom fill adapters well. I only support using my fill adapters which fit the best. I also have no idea what adapter he used. I know of some that blow out at much lower pressure than the Disco adapter will, those were made for bulk-fill conversion and were never meant for PCP. Many use them for that purpose which I think is extremely dangerous.
I'm on vacation and won't be back to my shop in Massachusetts until the first week of April. I will order a 2260 MB tube first thing Monday and have it sent to my Florida house so I can check it out sooner. Crosman isn't going to make a thin-walled tube for one poorly-selling model that requires all the internals to be larger diameter. Especially when those internals are common to quite a few more popular models. The cost would be prohibitive unless they were planning to make all of the 22XX CO2 tubes thinner. Obviously this would affect many of us drastically so we need to get the facts straight. I mean no disrespect to anyone but I just can't trust anything posted here until I test it for myself. I will post an update as soon as I know anything solid. I appreciate TKO bringing this up, especially if it turns out to be correct. Don't see how it could be but if I've learned anything in this life it's that literally anything is possible.
Bill
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I sincerely hope as many read this post and share it as possible, it's critical to the safety of building and working with Crosman PCP guns and conversions to PCP. There are typical variances and occasional manufacturing blunders that can affect the safety and compatibility of Crosman parts with custom components. I was under the impression this was widely understood due to my many posts about it on my website and in the listings there and on eBay for custom PCP tubes, fill adapters and tube assemblies. Hundreds of thousands have read this info over the years, tens of thousands have bought those parts and there hasn't been a single incident of a failure or injury in my ten years in business. Most GTA members are Magnum Airpower customers, many dating back to when I first started in 2009. Even so, from this issue coming up on GTA and recent questions from customers over the past couple months I've become aware it's not as known in the overall airgun community as I thought. Apparently that's the case even with many considered to be PCP/HPA experts including myself who was caught off-guard by this 2260MB tube controversy.
I originally addressed the 2260 MB tube post by TKO as a possible thin-walled version of that tube existing which many didn't know about including me. As the worlds largest and most popular seller of high-pressure components for Crosman PCP guns, that was critical to address immediately. According to Crosman that's not true, there are no thin-walled versions of the 2260 MB tube. (MODIFIED 3/23/2019 : I JUST RECEIVED TWO 2260MB TUBES FROM CROSMAN THAT HAVE COMPLETELY DIFFERENT FINISHES ON THEM. ONE IS THE NORMAL SMOOTH FINISH WITH A SLIGHT SHEEN TO IT, THE OTHER HAS A DARKER TEXTURED MATTE FINISH. THE DARKER MATTE VERSION I'VE NEVER SEEN BEFORE, IT'S OBVIOUSLY GROUND, NOT TURNED, TO CREATE THE TEXTURE WHICH ALSO REDUCED THE OD. IT APPEARS SOME WERE PRODUCED WITH THIS DIFFERENT FINISHING PROCESS LEAVING A REDUCED WALL THICKNESS. I WILL POST MEASUREMENT PHOTOS WITH MORE DETAILS FURTHER DOWN.) There are several other reasons that can explain the low-pressure failure TKO experienced, I address those below.
I called Crosman today to order a 2260MB tube and ask if there had been any changes in wall thickness. As I expected I was told there have been no changes to the 2260 MB tube. They are the exact same tube used for the 2260 but with different lettering. I ordered a couple anyways to check for sloppily manufactured threads beyond the normal variances I'm already aware of and any other possible anomalies. That part I will update as soon as I have the info.
As it says in my listings for my custom fill adapters, Crosman tube threads vary (by as much as .010") which causes fill adapters to fit well in some tubes and loose in others. For safety I have the threads on my custom adapters machined a little over-sized. This causes my adapters to fit snug in most tubes, extremely tight in some but never loose in any. The threads in many 22XX tubes like 2240, 2300KT, 2400KT 2250, 2260 and 2260 MB often fit my adapters as tight or tighter than with Discovery, Maximus, Marauder Pistol, etc. Crosman/Benjamin tubes tend to have a wide variance in the threads causing a fill adapter to fit tighter or looser. Many make custom adapters using a die instead of cutting them on a machine or machining them to 13/16-28 and assuming they will fit safely. This is a very bad idea because of this issue with thread variance. Threads cut with a standard 13/16-28 die or machined to that size will generally fit Crosman tubes dangerously loose for PCP purposes.
The cause of the thread variance is the tooling used to thread the tubes. It's in different states of wear from one production run to the next and it appears from the odd contours of the threads that they are cut with a custom made tool. Their worn tools tend to round-over and over-cut the threads. I still have no idea what fill adapter TKO was using but as I stated earlier I know of several that are sold by very popular sellers that fail at low pressures. I'll give two examples, even though I know this will cause me to receive a lot of flak over it. The first and one of the most popular is the bulk-fill adapters sold by Baker Airguns, also sold by others Baker supplies like Alchemy Airwerks. They are for bulk-fill, many use them for PCP, they can fail at pressures as low as about 5000 PSI with a Crosman tube. They work well in Don Cothran tubes because his tubes have much tighter-fitting threads than Crosman's. And that little hint there explains why Don's fill adapters also fail at low pressure in many Crosman tubes. His adapters are made to fit the tight threads of his tubes, not the sloppy threads in Crosman tubes. His threads are so tight, my adapters with over-sized threads won't thread into them at all. Discovery fill adapters fit most Crosman tubes pretty well but I've seen them fit a little loose on a few rare occasions. I've never had one blow out at low pressure, generally they fail in the 9000-10,000 PSI range or higher.
What I tend to think may have happened in the case of TKO's low-pressure blow-out, he either used a loose-fitting aftermarket adapter with a loose-fitting tube or a Discovery or Marauder Pistol adapter with unusually loose-fitting threads. Today I once again measured the wall thickness of a Discovery, Marauder Pistol, 1701P, 2250, 2260 and one of my custom 2240 tubes converted for PCP. All are exactly .875" OD and .0625" wall thickness at the back. The threaded sections at the front varied from .043" on the Marauder Pistol and 1701P to the tightest fit at .051" on the 2240 PCP tube of which I did nothing to the threads. The Discovery tube had only .045" from the OD to the thickest peak of the threads.
All of this presents no safety issue as long as your tube and fill adapter fit well together. I only suggest using my custom fill adapters made of 7075 aluminum or Discovery fill adapters which are made of stainless steel and tend to fit well in most cases. If a Discovery adapter fits your tube a little loose then don't use it. It can thread in easily but should not be able to wiggle at all once it's about half-way in. Marauder Pistol, 1720T, 1701P and Fortitude usually have the same aluminum adapter, only use it if it fits snug in the tube. Maximus models have been sold with either of those adapters, originally the aluminum, more recently the Discovery version.
I hope this clears things up for many of you and as usual I'm sure the nasty emails and calls will commence immediately! LOL!
Bill - Magnum Airpower LLC
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Obviously this would affect many of us drastically so we need to get the facts straight.
Bill, you are 100% correct.... It appears from your follow-up post that you are now 100% confident that there has been no specification or material change to the 2260 (or 2260MB) tube, and are willing to stake your reputation on it.... That's good enough for me.... I'll leave it to TKO22 to figure out what happened, hopefully he can enlighten us....
Bob
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Bill
Thanks for your hard work it is much appreciated Dan Sapp
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Thank you Bill, TKO22 and Bob.
I think this discussion still serves the same purpose: reinforcing using caution when using parts to synthesize a potentially higher pressure vessel than what was intended with specific information about Crosman tolerances. This is the exact type of discussion and content that lead me to join! I did not know about the different crosman fill plugs or tube tolerances. Thanks. That just decreased my overall safety margin of error!
My view of HPA is if you are intending to create something HPA you have to be paranoid about every step you take and research all parts, materials and procedures. Also research the failures to know the consequences of "doing it wrong". I'd dare say there are types of people that just shouldn't be undertaking it and maybe a little self-evaluation is in order (the measure once cut twice person). When you are building, it is also a good thing to second guess yourself and self-evaluate. I've made a few pressure vessels that I never put air in because I didn't have enough information on the mechanics and they looked like missiles ready to launch. However I intend to use my hydraulic pump for destruction testing at some point.
Sorry bloveating.
I just got my tracking from Crosman for my parts and the 2260 tube and I will post the wall thickness when I get it.
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Everyone's input is greatly appreciated.
The fact that there was a concern and it was reported then taken seriously by so many is a true testament to the members of GTA.
TKO for alerting to what he experienced, rsterne for sharing it here to make sure the awareness got to as many as possible, and I am certainly glad there was investigation into this by Magnum Airpower.
One can never be too cautious when working with HPA. Industrial variances in tooling and process were my initial thought, and Bills explanation makes perfect sense.
I expect mine to be delivered today, possibly tomorrow and will report my measurements ASAP.
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My new tube arrived today.
Ordered direct from Crosman on Friday 3/8/19
What I received is stamped 2260 on the right side. There is no "MB" reference.
Serial number laser etched on the left side reads 219500215
I measured in three places around the circumference of the tube and avreaged them out. No doubt a little egg shaped from the stamping process...
The OD of the tube measures .880
ID at the rear is .748
Rear wall thickness measures .065
Threaded wall section measures .048
*edit: there is a step or shoulder about a 1/4" inside of the front of the tube down past the threads.*
Curious as to whether I got a NOS tube and not one of the more recent in question.
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Thanks for those dimensions, Scott.... I am waiting for TKO22 to return, hopefully he still has the tube in question and can do similar measurements....
This whole thing is very strange to me....
Bob
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Bob, where was TKO's original post?
I know I read it before this one, but now can't find it.
Seems to me he said the stamping on his failed "MB" tube was on the left side... maybe I dreamed it.
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The only information I have is what I posted in the OP of this thread....
Bob
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I just found this warning from TKO22.... I have no first hand knowledge of this, but PLEASE check this out if you are considering using HPA on a gun equipped with a 2260MB tube.... Even bulk filling with CO2 would be questionable, as the safety margin if the gun is left inside a hot car would be less than 3:1.... CO2 can reach 1900 psi at 120*F....
TKO22 SAYS:
The Crosman 2260 air tube has recently been changed by Crosman.
The new tubes are marked: "2260MB".
These ARE NOT THE same as the old 2260 tubes. They are 0.049 wall and machine very differently than the old "2260" tubes (0.065 wall). The 2260MB tubes also have a hard step at the front threaded end that will make it very difficult to get it to seal with a Discovery fill adapter. The 2260 tubes are chamfered for a smooth squeeze on the adapter o-rings.
I have hydro'd a couple of the newer 2260MB tubes, and they failed at ~4100-4600 psi. In each case, the fill adapter blew out the front.
I have assembled about 50 PCP pistols and carbines over the course of 5-6 years, using the 2260 tubes and no failures reported. I wouldn't use a 2260MB tube except for a Co2 cartridge gun.
If this is in fact true, this thread should be made a sticky, IMO.... Stay Safe !!!!
Bob
I have three tubes in front of me:
A 2260MB, a Discovery and a Maximus tube.
The 2260MB tube wall is .049. OD: .863
The Discovery tube wall is .063. OD: .875
The Maximus tube wall is .065. OD: 874
Average of 3 measurements each.
Probably the same material as they machine identically, but not the same dimensions.
It would be a good idea to measure and verify dimensions with any 2260MB tubes you are considering for a PCP build.
Tossing my nickel in the pot. :P
" The 2260MB tube wall is .049. OD: .863" I'm surprised nobody caught the significance of these measurements. :D
.863" is within the tolerances of a 22mm tube (21.92mm), while .049" is within the tolerance for a 1.25mm wall (1.2446).
I wonder if TKO got hold of a Chinese knockoff tube. :o
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The only information I have is what I posted in the OP of this thread....
Bob
To put it bluntly... where did you find it?
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Somewhere on the GTA is all I can tell you.... I was searching for something else and ran across it.... I felt it was so important I copied it and pasted it into the OP of this thread.... I don't remember what the thread was that I found it in, sorry.... I do believe you are correct, that the roll-stamp was on the opposite side.... TKO22 is away ATM, but I'm sure he will be posting when he returns, and you can ask him directly....
Found it by searching here on the GTA.... https://www.gatewaytoairguns.org/GTA/index.php?topic=152894. (https://www.gatewaytoairguns.org/GTA/index.php?topic=152894.) …. Reply #11....
Bob
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Sorry, I knew that was in my original thread but it slipped my mind.
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(https://www.gatewaytoairguns.org/GTA/MGalleryItem.php?id=6289)
Had time today and measured walls of some tubes:
2 - older 2240 tubes (disassembled carbine to add to Disco tube and PROD trigger, maximus barrel...when have time)
1 - new 2260 (2260-004 not ordered as 2260MB)
1 - new Discovery (laser) tube
All were .065 with the disco tube being a hair smaller but within .008 error of my HF "last inventory reduction, going out of business sale" 20% off sale price calipers.
Front readings were also .049. Fill plug doesn't wiggle in all of them at 1/2 in and steps are pronounced as they should be intended.
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That is a good point... I ordered part number 2260-004 as well.
So Dan.... what was the serial number on your tube?
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That is a good point... I ordered part number 2260-004 as well.
So Dan.... what was the serial number on your tube?
219500204 which looks to be laser etched. Too bad they can't make the warning laser etched.
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Found it by searching here on the GTA.... https://www.gatewaytoairguns.org/GTA/index.php?topic=152894. (https://www.gatewaytoairguns.org/GTA/index.php?topic=152894.) …. Reply #11....
Bob
AH-HA!!!
So there it is...
Edited to add: If I recall correctly, the 2260 tubes were roll stamped on the right side, the 2260MB tubes are stamped on the left side.
I just KNEW I read that!
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219500204 which looks to be laser etched. Too bad they can't make the warning laser etched.
That is very close to mine I just received...219500215. So looks like 11 tubes off the line apart.
Makes me think it may not be "old Stock"
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That is very close to mine I just received...219500215. So looks like 11 tubes off the line apart.
Makes me think it may not be "old Stock"
So I'm wondering, Do they fulfill orders by sequential serial number?
I wonder when the roll stamp serial numbers stopped. THOSE would be old stock. The 2240s are stamped serials right where the valve screw holes should go.
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Probably not... but I would think they pull them out of the "bin" as orders are filled... And Surely they FIFO.
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Sorry I've been missing the fun here...
Returned Monday from a 4 day hunt to major flooding. Been dealing with it... when I can get there.
A few quick notes:
The fill adapter WAS a Discovery adapter. I only used that adapter for all my PCP builds as they are good quality and cheap.
I bought 3 2260 tubes from Crosman around late 2016- early 2017, as I have done for the previous 5-6 years. I noticed they were different from the tubes I have been buying and using to build my PCP conversions.
The roll stamping of the model and warning info was on the left side of the tube. They were/are marked 2260MB. There is a picture somewhere out on the internet of it.
I measured all three tubes and all three were oversize bore/undersize wall. I did weigh them, but didn't have another 2260 tube that wasn't on a build to compare.
That's when I posted a first warning about the differences. As I recall I posted on the old Green forum.
I had access to a very complex pressure testing facility as I was a sub-contractor on a couple of high pressure vessel projects. That company has since been sold to a foreign conglomerate and my access is limited now. My experience with pressure vessels spans small cold gas maneuvering vessels used in aerospace projects to very large 20K PSI accumulators used to stabilize offshore drilling rigs to compressed natural gas vehicle tanks.
I've attended to many dozens of pressure testing and destructive testing of all sorts. Fire, piercing, impact, turque, crushing, and over pressurizing to failure. Been there. Hydroing to failure is very anticlimactic... Pop. Gas Pressurizing to failure is epic. Hydro lets you see what failed. Gas failures demonstrate the real power of a blown vessel. Often the real reason for the failure can't be determined because of the collateral damage caused. (Case in point ... I gassed to failure two of Mike Melick's XS-60 PCP assemblies, at his request, and never could determine the failure point, but did determine the best way to blow one up. (Hint: not by exceeding stated working pressure...)
So the meat of the issue ...
Q. Are there 2260MB tubes that are out of spec?
A: Yes. I still have one at the shop.
All three were within a couple of thousandths of each other.
All had roll stamping on the left side and serial number on the right. I failed to check if the serial #s were consecutive.
All had a weird light "scalloped" marking at the threaded end.
I'm heading down to my range to see if the road is still closed. If not, it might be a few days til I get back to this deal.
Be safe all,
Mike
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I like to speculate in general to work all the angles. Maybe it doesn't help in this case because conjecture can make a conversation go anywhere. What I was thinking is all Crosman tubes start out as DOM steel from a supplier somewhere (they are not steel producers). Is it possible that they were somehow provided the wrong tube and their computer controlled lathe operation didn't notice the lack of chips in the fill end boring process of these tubes? I think only Crosman has the real answer.
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Mike, thanks for posting that.... The thing still being questioned by some is the wall thickness of the main body of the tube, ie what is it at the back, not at the front where it is threaded.... If you get a chance, I would appreciate it if you could photograph the tube you still have, remeasure it at the back (ID, OD, wall thickness), and document it.... Measuring the ID of the threaded section, and photographing it as well, would help, of course.... If you have no way to post those photos, you can send them to me at airgunbob at gmail dot com and I will host them here via my Photobucket account for all to see.... This mystery, IMO, is still that.... and we need to try and get to the bottom of it....
Bob
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Mike, thanks for posting that.... The thing still being questioned by some is the wall thickness of the main body of the tube, ie what is it at the back, not at the front where it is threaded.... If you get a chance, I would appreciate it if you could photograph the tube you still have, remeasure it at the back (ID, OD, wall thickness), and document it.... Measuring the ID of the threaded section, and photographing it as well, would help, of course.... If you have no way to post those photos, you can send them to me at airgunbob at gmail dot com and I will host them here via my Photobucket account for all to see.... This mystery, IMO, is still that.... and we need to try and get to the bottom of it....
Bob
I have a few minutes to respond to the 2260MB stuff.
FYI .. I've been dealing with the epic flooding we've had here in Eastern Nebraska. So, I'll have to post things as I have some time.
Firstly, Some measurements I took tonight:
2260MB Tube:
Breech end... OD: .8640, Wall: .0515, .0555 (taken 180*)
Threaded end... Major thread: .0325, .0350
Thread depth (from end of tube): .4185
Location of hard "step" (from end of tube): .6545
I did try to take some deep internal ID measurements using a shotgun bore gauge, but the results were all over the place. Might be tired old me, or tired old bore gauge.
Appearance:
The 2260 tube has a different, shinier, less blue surface than the Discovery tube.
The 2260 tube has a couple of linear "scallops" at the end of the threaded end.
The 2260 tube has a pronounced "step" from the threading to the major ID.
The roll stamping is on the left side. Serial # lasered on the right rear.
Discovery has the serial number dot-engraved (not lasered) on the bottom of the airtube.
The warnings and "Discovery" text are laser etched on each side. My Discovery is re-assembled, and I don't want to take it apart again, but the OD at 1/2" from the end of the breech is .8750 and .8775, depending on where I measure.
I hope that will do you for now.
PS: I found a picture of the hard step past the threads on my development/database server. I'll try to link it.
Step in the threaded end:
(http://www.tko22.com/2260mb_1.jpg)
Roll stamping on the LEFT side:
(http://www.tko22.com/2260mb_2.jpg)
Try the links now... should display. The links will only be available for a limited time as they are not in the correct directory structure for my production server.
Bye!
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If I understand your measurements, the ID at the breech end would be 0.8640" - (0.0515+0.0555) = 0.0757".... That is a really strange set of measurements, not matching any common North American tubing standards.... The OD is close to 22mm, but the wall thickness is a lot less than 1.5mm (0.059")….
Are the dimensions you gave for the "major thread" the wall thickness measured from the ID of the thread to the OD of the tube?.... If so, that would indicate an ID for the threads of 0.8640" - (0.0325+0.0350) = 0.7965".... Since the minor diameter of 13/16"-28 female threads is supposed to be 0.774-0.782", there would be far less thread pitch engagement than there should be.... In fact, if the fill fitting was near the minimum OD tolerance of 0.8048", the total thread engagement would only be 0.0083" (just over 0.004" per side)…. Even in the worst case scenario, with both male and female threads within allowable tolerance range, the total engagement should be 3 times that much.... I just measured the three 22XX tubes I have here that are not assembled, two measured 0.774" ID and the other 0.777" ID for the inside of the threads, well within tolerance, in fact two at the minimum, and the other less than mid way through the acceptable tolerance range.... Even with a fill fitting at minimum tolerance on the OD, the total thread engagement depth would be at least 0.028"....
It is not surprising that you experienced the fill fitting blowing out of the end at 4100-4600 psi.... However, we are still left with the mystery of what these tubes are.... did Crosman have a "bad batch" of tubes?.... Were they supplied with 22mm OD tubing that was supposed to be 1.5mm wall and was undersize.... instead of 7/8" x 0.065"?.... How did these tubes slip by their quality control?.... Were they made offshore instead of in the USA?.... The roll stamping on the left side seems to be a key to identifying them.... at least hopefully that is the case....
It might be a good idea at this point to notify Crosman of this situation and ask them if they have any ideas.... Bear in mind that even if the tubes were thinner wall, they would be fine for using CO2 cartridges as intended, there is NO safety issue here when used as intended....
Bob
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OK folks, so I finally got to the bottom of the thin-walled 2260 MB tube mystery. As I originally suspected and was further informed by Crosman they did not make any tubes from thinner tubing or change any of the specs. Well, not intentionally anyways. What did happen, which completely backs up the original post by TKO, is they finished a small number of those tubes with a ground texture. Those tubes have a matte-black rough-textured finish. The standard 2260 MB tubes are smooth with a more obvious sheen. The grinding process on the matte tubes removes varying amounts of metal producing a slightly thinner wall. This type of ground texture is common with Discovery and Maximus tubes but never removes enough material, as far as I'm aware of anyways, to affect the wall thickness significantly. These 2260 MB ground tubes have much more thickness removed and are inconsistent with random thinner and thicker areas. The bottom line is, 2260 MB tubes with a ground finish are not safe for PCP conversions, the smooth non-ground tubes are. None of the tubes I've ever sold have this issue and I was unaware these ground-finish 2260 MB tubes existed until I finally got my hands on one. If you have any 22XX tube with a ground finish don't use it for PCP, HPA or bulk-fill conversions where the tube is pressurized. It could have thin spots that make it unsafe even at lower pressures. The ground tube measured in the photos below wouldn't be safe for bulk-fill, it's unevenly ground with random thin spots along it's length. It never crossed my mind the finishing process could be the cause of this issue but like I said in one of the earlier posts, anything is possible. I don't give up on an issue this important until I've discovered every variable and every exception.
The attached photos were taken from two 2260 MB tubes received from Crosman end of last week. They have consecutive serial numbers but were obviously not produced in the same batch, the numbers were lasered on later. Interestingly, the non-ground tube has a thicker wall thickness than I've seen before, it's measuring .0660" compared to the .0625" I generally find. The first photo shows the ground tube on the left and non-ground on the right. Photos 2-4 are the ground tube, 5-7 are the non-ground. The non-ground tube arrived with a dent at the tip of the threaded end you can see in the photo so I measured it back further. The label at the bottom of each photo explains what's being measured.
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Your second pic posted makes no sense.... The reading of 0.6650" for the OD is impossible, that is smaller than the ID of a 22XX tube....
Otherwise, good detective work, Bill.... and I agree with your conclusions.... I also talked to a Crosman engineer, and they have no record of any tubes being produced that were thinner wall.... but the outside ground finish, if overdone, could be the culprit, for sure....
Bob
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Do these ground surface tubes have the tell-tale "2260MB" stamped on the left side that TKO described?
That alone seems odd and may be a clue to the origin of these issues.
Did Crosman have any knowledge of that change?
*Edit*
I see 2260MB on the 344 serial number tube magnum posted.
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It so happens that last weekend I had a customer (local) bring me two of my real early 2260 conversions for a re-seal, and while looking the tubes over:
Both had the roll stamping on the right side (both marked 2260 ... not 2260MB).
But one had the serial# on the right side and one on the left. So trying to identify what is what by where the stamping/serial # is might not work every time.
Interesting ... the out-of spec tubes I had were finished in a much more "smooth/shinier" finish than I had previously received. So again, I think the only way to identify a out-of-spec tube is to measure it.
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Did anyone notice that BOTH the 2260MB tubes that Bill posted in his photo above were roll-stamped on the LEFT?.... Both were stamped 2260MB, the smooth (dark) one was within spec, the one with the scratchey, ground finish (appears lighter because it reflects the light differently) was not.... THAT is the only visual difference between them....
I just looked at all my 22XX tubes, all of which are at least 5 years old, and all of them are stamped on the RIGHT (2240, 2250 and 2260) and have a smooth exterior finish with no "scratches" from being ground down on the outside)…. They have a nominal 0.065" wall, per the spec. of the tubing they are made from, OD of 0.875", ID of 0.745", within manufacturing tolerances, and NO indication of machining, inside or outside, except where drilled or slotted, or bored and threaded for the front plug….
I'm guessing that "all" the 2260MB tubes are stamped on the LEFT, and that SOME of them are ground on the outside, and that SOME of those may be problematic if subjected to internal pressure.... Measuring may be the ONLY way to identify them, unfortunately.... I personally would reject for an HPA or bulk fill project any Crosman tube that had a sanded or ground appearance, and measured under 0.870" anywhere on the OD.... now that I am aware that some tubes are smaller than that.... I would also be careful to check the fit on any front plug relative to the threads in the tube, to make sure that both male and female threads were within specs, before using the tube as a pressure reservoir.... Proper anchoring of the valve is required, of course....
Bob
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Did anyone notice that BOTH the 2260MB tubes that Bill posted in his photo above were roll-stamped on the LEFT?.... Both were stamped 2260MB, the smooth (dark) one was within spec, the one with the scratchey, ground finish (appears lighter because it reflects the light differently)
I did , see my posted comment two above yours. ;)
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All,
Bob (rsterne) reached out to me about this issue. All I can say is that our drawings callout the same raw material for the 2260 Disco, and Max (among others).
HOWEVER, modifying a CO2 gun to HPA is at the risk of the person doing it. The tube should be measured, inspected and evaluated before converting it to HPA or bulk fill. There is a large difference between holding a CO2 bottle and gas directly. Again these modifications are at your own risk!
Personally I love what you all are doing in modifying our guns just please be safe about it!
Thanks,
John
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Thanks for your attention John.
Please come back soon!
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John, thanks for jumping in with your comments.... much appreciated....
Bob
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Thank you Bob for "Raising the Flag" and contacting Crosman direct.
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Bob, didn't realize that photo had the misreading on the micrometer until you pointed it out. I was on vacation when I posted those and was kind of rushed to get them up. The wife wasn't too happy I was "working" instead of paying attention to her. It's hard to work under threat of bodily injury! LOL! Deleted that photo, wall thickness and difference in OD explained below.
UPDATE: TOOK A CROSS-SECTION PHOTO OF THOSE TUBES SIDE BY SIDE. THE TUBE ON THE LEFT IS FULL-THICKNESS, THE ONE ON THE RIGHT IS GROUND. WHEN I MEASURED THE WALL THICKNESS FROM THE OD TO THE BOTTOM OF THE THREADS, IN OTHER WORDS THE ACTUAL WALL THICKNESS AROUND THE THREADS, IT'S .009" THINNER ON THE GROUND TUBE WHICH IS CONSISTENT WITH THE OD BEING SMALLER BY .017" - .022" DEPENDING ON WHERE YOU MEASURE. YOU CAN ALSO SEE THE DIFFERENCE IN OD DRAMATICALLY WITH THE TOPS OF THE TUBES ALIGNED, THE BOTTOMS ARE NOWHERE NEAR EACH OTHER.
Bill
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I just finished converting my 2240 to HPA. I used seamless stainless tubing to make the main tube. It is .875 O.D., .745 I.D. with a .065 wall. The tube is also longer at 10". I pumped it up to 3,000 psi with no problem. Got a whopping 993.4 fps with JSB 14 grain pellets!
(http://)
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Here is a pic of the chrony. I couldn't put both pics in the same post.
(http://)
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Show Off!
;)
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Could we please keep this thread on topic, regarding the safety of the 2260MB tubes with the thinner wall and ground finish.... Please start your own thread to brag about results (nice job, BTW)…. ;)
Bob
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Good to know, glad someone is figuring this out and letting us know. Good Job!