50 bmg
http://www.hevanet.com/temple/index.html Neck turning in general is to make neck wall thickness the same on all cases. As for the minimum thickness for the neck wall on a 50BMG i have no idea.
I would guess .014" is the minimum wall thickness. Just a guess?????
http://www.hevanet.com/temple/MatchPrep.html Quote:
" Neck turning
There are a number of reasons to neck-turn your brass. Some benchrest rifles are cut with extra-tight chambers and require neck turned cases, just to chamber - I'm going to assume that if you have such a critter, you know all about it. For those shooting 'factory' rifles, there are still some advantages to be had. Neck turning uniforms the wall thickness. A uniform wall thickness results in more uniform release tension, the case lets go of the bullet evenly, directly contributing to accuracy. Uneven tension while seating bullets can cause the bullet to cant, increasing runout. Finally uniform necks present a uniform amount of tension for each and every case, minimizing one more potential inconsistency.
To determine how much to neck turn, I will take four or five cases from the lot to be prepped and set my neck turning jig to just scrape some brass off. I'll turn all five and then examine them. What I'm looking for is a depth that cuts about 75% of the way around the 'average' shell. It may cut all the way around one, and barely cut at all on another, at the extremes, but for three of the five, I want 75%. Now on this first pass it's unlikely that I got there (if I did, I was rushing things...) so I'll adjust the cutter in ever-so-slightly and try again. I repeat this procedure until I get the depth I want. (~75% on most of the cases.) If you use the K&M, or another trimmer that allows you to measure your turned thickness, you can just adjust right down to your desired thickness. (Probably .001" more than the thinnest measurement from before, although maybe the same as that measurement, or a thou under, there's no magic here - go with what seems right to you, and experiment. Just remember that you can always take more off, you can't usually put any back...
I've motorized my turning setup, by using my drill press. It works just as well, if not quite as conveniently, by hand. Note that my drill press has a DC motor and can be turned very slowly - I go probably 30 rpm. Note also that the trimmer isn't actually clamped in the photos, it's 'floating' in the clamp jaws - this allows it to align naturally to the shell." Quote: