I believe all the weatherby rounds are freebored chambers, not sure about mark Vs in std calibers. My experience is that the wby factory rounds shoot so well most of the time, the only reason to reload is for cheaper shooting at the range. My 300 is a little more finicky though, haven't found a load to equal factory 180s that get an inch if I'm good that day or 1/1/2-2 if I,m too quick on the trigger. A 257 with 120 NPs and a 340 with 250 NPs are under an inch any day of the week. All at 100 yds of course. So basically I gave up and use factory stuff to hunt and just do a little reloading for the bench. I would follow ringman's advice and load for the magazine and smooth feeding.
