Necking down.

[grovey]

I read the neck measuring thread yesterday, and had a question along the same lines. In the OP'S case he was talking about a factory .308 chamber being large . My question is about the same case family. In the case of a .243, or even a .260 for that matter...

What are the pros and cons of necking down 7mm/08 brass to take up some of the slop in a non tight neck factory chamber? Anything to be gained besides more prep work from this thinking?

 

[Dusty Stevens]

Are you asking to get thicker necks is what youre trying to do?

 

[grovey]

Yeah, it would have to be thicker.

 

[Dusty Stevens]

Theyll be thicker but it may not be enough to be worth the hassle

 

[grovey]

Gotcha, thanks.

 

[Shaggy357]

It will cost you about $.15 and half hour to find out. Size the case, seat a bullet (no powder or primer), blacken the neck with a candle, and then chamber it in your gun. See how she fits.......

 

[Brians356]

FWIW I formed down a few 7x57 Mauser cases to 6mm Rem, and the neck walls thickened quite a bit. I have my mic measurements at home, only I'm in office now. But I can tell you this: To turn my 6mm Rem case necks for 100% clean up, I need to go down to .013" wall. Using 7x57 formed down to 6mm, I can turn them to .015" and still clean them up 100%. And that will leave me with only .003" total loaded round clearance in my R-700's .276" chamber.

So I think your idea is a "go". As mentioned, try it on a few culled cases first.

PS I am also looking into forming 270 Win from 30-06 for this very reason.

 

[timeout]

I have necked down Lapua 30-06 brass to 25-06. The necks thickened quite a bit, I don't remember the exact amount. I did need to neck turn the brass to obtain clearance with the chamber. (I wanted to turn the necks anyway to make them even) I had used a custom PTG reamer though for my 25-06. Perhaps for a standard factory chamber, I would have had enough clearance? I'm not certain that you will gain enough to be worth the effort. I would recommend that you cerrosafe the chamber to get a good accurate measurement of your chamber's neck diameter.

 

[Brians356]

I will experiment on a few 30-06 cases to verify any gains before obtaining a larger number of cases.

WRT checking neck clearance, a fired case neck can't really be any larger than the chamber, and is usually about .001" smaller. But I also use pin gages to probe the neck, and if the two methods seem to agree, and I am not getting too greedy (e.g. leaving .003" estimated clearance) then the final sanity check will be to ink the neck of a dummy round and check for chambering resistance and any witness marks.