thank you very much Martin! awesome explanation, I appreciate that. I didn’t know this R17, very cool desing! it looks like much more complex to complete, but much more reliable and durable too! In the end I got my hands on some 5mm ID and 8mm OD tubes so I’ll probably start with a barrel liner to put in a null for a quick project, but that OD12mm ECM and in general the R17 .22LR looks very promising! It will be for sure my next big project when I get some time edit: just understood the R17 is your own creation, very big compliments from my side! It is the most serious fully diy semiautomatic .22 handgun I have seen yet. Thank you for sharing this and adding value to this community! we need more people like you <3

just noticed that V3ECM is meant to build .22lr barrels from 8mm OD steel tubes, not 12mm. so there is no way in making solid steel barrels for handguns? must use a barrel liner mandatory?

thank you very much for the detailed explanation! I think 12mm OD pipe looks the safest (though for sure heavier than carbon tube), and I don’t really like smoothbore, I prefer accuracy even if it’s just a .22