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I'd like to try to make some 338WM from 300WM.

Any good pointers?

ANY/ALL Input Welcome.

Thanks
BloodGroove4570
 

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Ray, it should work but they probably will be 10 or 15 thousands of inch short. Lube the heck out of the inside neck on the .300 WM first. You are sizing up in caliber so neck thickness will be fine. Just remember when going down in caliber that the neck will thicken and may require reaming or outside turning. I always measure the case neck with bullet seated when sizing a case down in caliber, i.e., .308 to 7mm-08 etc. Most reloading manuals with drawings give the dimension thickness with bullet seated. If the neck with bullet seated is thicker than listed, you could be chambering a bomb as the case mouth will not release the bullet quick enough and chamber pressures will skyrocket to self destruct levels. It won't happen however in you scenario of going up in caliber.

358 Win

PS: The case being a bit short won't hurt a blessed thing in your chamber. I've done it several thousand times in my .358 Winchesters made from .308 Winchester brass.
 

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The 300 Win Mag case is LONGER than the 338 Win mag case.
True, but it will still shorten when resizing up to 338 WM. The 7mm-08 case is longer than the .358 Win case but still shortens below .358 trim to length when sizing it up to .358 Win.

358 Win
 

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.

Hey Ray,


I have found that new unfired Winchester brass work best for your project, once fired brass has a higher failure rate.

Cases .010 short doesn't matter........you get more firings before needing to trim again..:biggrin:
 
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