Can anyone enlighten me as to the rifling twist rate of a BRNO ZKK 601 in caliber .223? The only information I have been able to find indicates that it is 1-13", which seems rather unlikely.

It would be CIP specs I believe. I recently picked up some unchambered Heym blanks that were listed as 223, and near as I can figure the twist works out to something like 1-11.75" or so. It would most likely be 11.8 twist which would be 1-30 centimeters.

1:12 for the ZKK 601

CZ USA changed it from 1:12 to 1: 9 ? circa 2014

Thanks Matt and ALF for the rapid response!

I think Zastava was also using the slower twist and changed only recently.

Bill Warren (xausa)