Forming .243 brass from 30-06 or 270 cases

[kludge]

"...screw the die in a 1/8 of a turn at a time size the brass, try to chamber the brass, screw the die in 1/8 of a turn, size the brass," etc.

Given that 1/8 turn moves a die about 9 thou and that's several thou more than the full max to min range of headspace I would suggest making die changes of not more than maybe half that much. ??

You are correct, thanks for pointing that out.

 

[Sturmcrow]

I managed to find a fired case. The neck diameter was 0.276", compared to 0.271" in my resized and loaded cases. Based on the 37% neck thickness quoted earlier, does that mean that resizing from 308 cases will be give me the results I want?

I am unclear if I should aim to have my final loaded neck thickness at 0.276", or if I should back off a bit from that. I know that the actual chamber neck diameter will be a bit more than that due to springback.

Also, is it true that resizing from 308 will yield cases that are a bit short? I know that 308 cases start out shorter than .243, but I'm unsure if sizing the neck down will shorten or lengthen the case length. As someone mentioned earlier, my cases do not grow anywhere near as much as rumor would have one believe. After three (max by book) loadings, I still have a couple with a bit of neck that hasn't been touched by the trimmer.

 

[kludge]

0.276" is the correct neck diameter for a .243 Win (at least that's what all the cartridge drawings say). Your .271" loaded case means you have a neck thickness or 0.014"... not necessarily a bad thing...

You could look for a different brand of .243 brass with thicker walls/necks, but your measurement means that your chamber (at least in the neck) appears to be well within spec.

At this point all I can say is try it... it sounds like that's what you want to do anyway. But before I did I would spend $20 and cast the chamber (or if you have a friend with a set of pin gauges) to *know* what your chamber dimensions are before you go through all the trouble of reforming and neck turning brass. This will keep you out of trouble by having necks that are too tight in the chamber.

If this is a hunting rifle then 0.003"-0.004" would be the minimum clearance and 0.005-0.006" can be fairly "normal". For a target rifle 0.003" clearance would be fine, many would say 0.002" is ideal.