Re: bushings for 300 rum question
I had the same problem - the "best guess" bushing was wrong and I'll not be using it again! So, yes you make a good point.
You can mike neck thickness if you have the right micrometer to do so, mike the bullet od and do the maths.
Or, borrow a die, or visit someone with one, and seat a bullet and measure od of the loaded round as recommended.
I speak under correction, but the "factory" spec for my .300 WM was around .340 recommended I think. I can check it if I can find the e-mail. If you ask the question at either Sinclair or Redding you should get a reply.