Any real difference between Fed Gold Medal .308 and Gold Medal 7.62x51 brass


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Detritus
November 15, 2012, 07:43 PM
I have a total of 100 pieces of once fired brass from Federal Gold Medal factory ammo. 80 pieces are ".308" GM (GM308M), and the remaining 20 are "7.62x51" (GM762M2).

My question is.. Other than cosmetic differences*, is there enough difference in these two subtypes of brass to segregate them? or can i simply treat all 100 pieces as being the same?

*the "7.62" brass is unpolished, has a simple "FC '11" (no NATO mark) headstamp and (felt like it had, mildly) crimped primers. the ".308" is polished like most commercial brass, has "FC 308 Win" headstamp, and no crimp.

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dannewberry
November 15, 2012, 08:11 PM
You can weigh the cases, and check internal volumes and compare.

The Federal brass will work better for you if you'll anneal it, even though it's once fired. It's hard to get consistent accuracy with this brass, but folks who anneal have reported acceptable results.

With the thicker brass of the FC cases, your usual accuracy nodes will be reduced by 1 to 2 percent... For example, the 168 grain Matchking with 4064 pushing it will favor 43.5 grains in FC cases (Federal's old recipe for the GMM before the ATK era), but in Winchester the accuracy node seems to be in the mid 44's... around 44.5 by most reports.

These numbers are relative, and of course you'll have to poke around on your own to see what powder charge works best...

Don't drive the FC cases too hard... work with low to mid range pressures and it'll last you a few loadings, most likely.

Dan

Detritus
November 15, 2012, 08:29 PM
Don't drive the FC cases too hard... work with low to mid range pressures and it'll last you a few loadings, most likely.

Really just farting around with these until i can get a new FL resizing die (too little lube, don't wanna talk about it...), and can go back to using the Winchester brass i'd been using up to now

You can weigh the cases, and check internal volumes and compare.

cases are all int the same 176-178gr weight range with no bias toward one or the other. they're all deprimed currently so i can't do a water volume test currently

dannewberry
November 15, 2012, 11:35 PM
I'd say if they're the same weight, that's pretty good evidence that the internal volume is close enough to go on and use them as a lot--especially since you're not going to be pushing the envelope of pressure anyway.

I prefer Winchester cases myself, but whenever FC cases come my way, I find some use for them one way or another. :)

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