submitted 2 months ago by Skanda@fosscad.io to c/3D2A@fosscad.io

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Hello everyone.

I've been following the community for many years and have built a few models thanks to the superb information provided by everyone.

I know this topic keeps coming up especially for non-American makers.

I'm familiar with ECM, I've done the FGC-9 and it turned out very well. I've tried the .22 rifling button from the guy in Ukraine with dubious results (I've NEVER seen rifling buttons on AliExpress). I can see the marks, but I'm not certain they're deep enough. This was for a Harlot build. I then did a .22 barrel for the Dirty Harry build using ECM with mandrels in the Professional Damage ECM Pack. I think that turned out quite well and was surprisingly easy.

I've used 12 mm OD 5.5 mm ID hydraulic pipe from AliExpress which seem to be readily available, but I was trying to find a suitable pipe with a smaller OD.

The best source I've seen is McMaster which carries a 3/8 inch, 0.216" ID which is rated for 15000 psi which seems perfect, but it's like 80 bucks a foot and I haven't even looked at shipping outside America.

I have not found any pipe on AliExpress with a 5.5 mm ID less than 12 mm. I usually look for 42crmo or 'explosion proof' in the description.

I do have access to a small lathe. How safe would it be to turn down 12x5.5 explosion-proof tube to say 8 mm OD for a .22 barrel? Would it support the pressure?

TIA

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[-] johndoe@forum.guncadindex.com 3 points 2 months ago

OK so there are some misconceptions floating around..

the 8mm liners are supposed to be pressed and glued fit into much thicker steel tubes and do NOT have sufficient wall thickness. It is a bad and potentially dangerous idea to put them into 3D printed soft polymer. Using such thin liners is a very bad practice that has become common by designers who might be proficient in CAD but lack the neccessary knowledge in metallurgy and physics. These designs WILL fatigue crack and go boom after a while if used with HV / high pressure ammo.
Machining a 8mm diameter steel tube down to 1mm wall thickness on a lathe is difficult for amateurs because likely there will be missing support in the middle of the tube and will likely bend it.
It is much better to change the design from 8mm to 12mm barrels and/or provide that as an alternative. Also please DO explain to the US bases designers that, by intentionally thinning down their designs to 8mm liners, they effectively prevent all others non-US people to use their designs, which is bad and contradicts 3D2A philosophy. Also, who sais that the US bros won't get in a situation where they'll need to use hydraulic 16mm or 12mm tubing?

[-] Skanda@fosscad.io 1 points 2 months ago

Thank you so much for this information. It has always bothered me when metallurgy isn't part of the discussions.

The Dirty Harry is designed for 8 mm liners and has no provision for adding an external sleeve. Fortunately, I can't get barrel liners so will never test it like that. The DH does include a Proto Barrel design which accommodates a 10 mm OD tube which more closely matches the McMaster 3/8 inch tube which I think would be safe.

12 mm OD tubes really do seem to be the most readily available. I'd feel comfortable turning down 12 mm to 10 mm on a lathe, but you're correct, 8 mm seems way too thin. It could be done with a steady rest, but I'd be worried about the pressure.

I'm really not a fan of buttons, I think ECM is much more convenient.

[-] johndoe@forum.guncadindex.com 2 points 2 months ago

You're welcome.

With rifling buttons you need at least 1x the diameter as wall thickness.

So for 9x19, you'll need a tube with 8.8mm inner diameter and at least 1 inch outer diameter.

Industrial 9mm barrels are deep drilled into 30mm and sometimes 35mm thick CrMo rods, rifled and then turned down to their final diameter.

That's why ECM is so interesting commercially and also for DIY.

Btw. barrels are rifled in QT condition where tensile strength is highest. They are then, after rifling, stress relieved in vacuum furnaces.

Mark Serbu has some videos on Rumble about the process.

[-] FieldExpedient@forum.guncadindex.com 2 points 2 months ago

It should. Brownells 22 liners are about 8mm OD. That said, there's a beta over at BLC that uses a drilled bolt for a barrel.

If I were turning it myself, I'd leave a little more wiggle room. 1mm wall thickness feels a little sketchy to me.

[-] Skanda@fosscad.io 2 points 2 months ago

Ok, thanks. I don't really know how the strength is affected by machining. Metallurgy is kind of a black art to me. I'll have a look at the drilled bolt information. Do you know of they heat-treat anything to improve the strength?

[-] FieldExpedient@forum.guncadindex.com 1 points 2 months ago

There's nothing about heat treatment in the current documentation. Just drilling and ecm the rifling/chamber.

[-] johndoe@forum.guncadindex.com 2 points 2 months ago

btw I think Aliexpress has removed the buttons but you can find them on Temu (and sometimes on Ali again) with the following words

helical 6 flute reamer

Temu sometimes has them simply as rifling buttons.

this post was submitted on 02 Feb 2026

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