I'm working on getting parts together for my first custom rig and need some help. I'm going with 300 RUM and trying the 200 accubond and matchking, and possibly the 220 MK. What twist should I go with for this weight range? I know a faster twist is needed for the heavier bullets to stabalize them, and that too fast at twist at higher velocities will cause lighter bullets to spin apart? Is this a concern in bigger bore calibers? What about groove selection? Again, I'm just getting into this long range stuff and custom builds, so I'm spongin up any knowledge you can give me. Its takin' me some time getting things together and putting dollars together (I'm a school teacher) but I want to build my first one right. I've got several things together, mainly just reloading stuff for the RUM that I didn't have already, jewell trigger, badger base and rings, rem action, so I'm getting closer! Looking at a barrel blank next to send to the gunsmith when I get it all together. Thanks again for your help!