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Hi all!

I am forming .243 brass from once fired .308 military brass by running them first trough a 7mm-08 size die, then a .243 size die. The only thing I am concerned about is that when a bullet is seated, the neck diameter measures .277, rather than the spec of .275. A prepared dummy round cambers with zero resistance (just drops in my break action H&R). Should I be concerned?

Thanks!

Vince Warde
 

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neck

Hi
If you load a couple...shoot one and check if you have clearance...Try to slip a bullet into the neck, it should slip in easily!!! The case needs to "let go" of the bullet. But I would suggest that you outside neck turn the cases, anyway. It will help your accuracy!!! Just turn the necks enough to just get a cut all the way around. You will find one side thicker that the other.
Good luck
jim
 

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Forming .243 win cases from .308 military b

I think I'd outside neck turn the brass as after the forming process the necks are going to be thicker, and probably longer than normal.
 

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Forming .243 win cases from .308 military b

I'd trim to the specified trim to length and them outside turn them to spec. The .243 has a tendency to grow when fired due to the angle of the shoulder and the shoulder area.
 

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Forming .243 win cases from .308 military b

My brother ran into all kinds of pressure problems necking .308 cases down to .243. This was with starting loads. So when I got a .243 I bought an attachment for my case trimmer to turn the out side of the necks down.

I have never used it. Bulk brass became cheap enough that I stocked up on it. I still hang on to the attachment just in case I might need it some day.

There must be a critical point in necking down cases that the problem develops. I have necked .30-06 cases down to .277 without a problem.
 

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Forming .243 win cases from .308 military b

The only way to know for sure is to do a chamber cast, my handi 243 did seem to have a loose neck as wellbut I sold it off to buy a 270 before I fully go into reforming 308 brass.

You could also get an indication of the neck size by measuring fired cases here would be spring back of course but you could get an idea.
 

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Forming .243 win cases from .308 military b

I have 2- 243s, an encore and a savage 110. Neither has encountered any problems chambering or pressure, with necked down mil 308 brass. The necks end up a bit short but usually stretch a bit after fireforming. In my encore the loads are actually more accurate than in commercial brass. I have yet to turn any necks. I do my initial sizing with the 243 seating die (stem removed). That insures that the shoulder is not set back to far. Then run through the 243 sizer. It leaves a little bump in the shoulder that is smoothed out after fireforming.
 

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Forming .243 win cases from .308 military b

Dakotashooter2: Like the post and saved it for my .243 loading notes. May try it one these days.
 
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