30-223 or also called 30 Apachi. die set ( new ) used once to form a dummy round ( not incl) See pics to compared to a 300 BO auction includes 199 unformed basic Starline brass. These are hard to obtain also in NZ and expensive. I've attached pages from an article Gun Digest ( 1986 ) The plan was to rebarrel my Blackout to send a flatbase 110 vmax down the tube in a 1/17 twist barrel. I ended up sticking with the 300 Blackout ( budget effect of co-vid ) You can source a reamer for this calibre from USA or get a gunsmith play with exsisting 223 / 30 cal reamers . This would be a super efficent round with less muzzle jump and subseqently retaining sight picture on target. Finally if your after something different from the crowd this could appeal Enjoy the attached article. Thanks for looking