Wow. Well done @grandpamac. One of our sons regularly shoots his Howa heavy barrelled 1:8 twist out to 500 using Belmont 77 gr. I have the same rig but should perhaps use my Tikka Forest T3X 6.5x55. With handloads and off the bench I’ve managed cloverleaf results at 300yds. Sadly, I can no longer shoot prone after a lower back ‘weld’. The nearby Te Puke Club isn’t too far away, so I’d better investigate it as a challenge for ‘23.
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