I have a CZ 550 American 6.5x55 with a CZ stated barrel twist ratio of 1.86. I recently started hand loading. I'm getting exceptional accuracy with Berger 130 grain Hunting VLD's but am having trouble finding an accurate load using 140 grain Sierra GameKings. The only factory ammo I've used is the PRVI 139 grain bullets and they were very accurate. I read somewhere that you need a 1:8 twist to stabilize 140 grain bullets. Is that pretty much true or is it hit or miss with 140 grainers in a 1:9 twist? Will some rifles not stabilize 140 grains period and then some rifles stabilize some 140 grain bullets but not stabilize others?
Last edited by cdb; 04/30/14.
