Guys Im still trying to get that damn Semi Auto working and having a hell of a time trying to source any Aluminium or Carbon Fibre Tube here in Australia with a 6mm ID!??.
I bought a Carbon Fibre Tube I was told had 6mm ID but when I got home it had a smaller ID so is useless to me

.I looked at a few Hobby Shops but again the Carbon Fibre Tubes said to be 8MM OD x 6MM ID all had smaller ID size and all the Brass or Aluminium Tubes were not the right size either and would have way too much blowby for my liking.
I dont know why its so had to get Tube here with 6mm ID!!??, there was a link on here a while ago of someone saying to use Carbon Fibre Arrow Shafts but I cant find that thread now?.Though from memory they were expansive.....