Hi all - HELP!! - can anybody point me at a reliable and not TOO expensive source for .17cal barrel blanks. .17HMR/H2 I suppose. I want to build a sub calibre .177 airgun at high muzzle velocity and need a tighter twist I think. If it's in Europe, better still. Nothing OTT or extra special - I have to slim it down to 16mmOD too. Slimmest I can find at the mo' is Walther at 23mmOD. 24" would be nice - Longer OK too. Green Mountain are cheap though. Open to all advice and pointers. At the moment I'm running a Walther polygonal and it's OVERSIZE - about .179 (and a bit).