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Discussion Starter · #1 ·
O.K. I've been gathering pieces to put a bolt gun together in .308, hopefully sometime in the next couple months. My friend has the tool shop and equipment but neither of us has actually re-barreled anything. I have a Winchester 670 currently in 30-06 that has stepped forward for the project. I have a new #7 contour Shilen CM 1-10" .30 barrel and just ordered a reamer. The reamer is actually a new Manson but is labeled 7.62 Nato. I did this just to muddy the waters some more I guess. I have read as much as I could stand on .308 vs. 7.62 but really come away as dumb as before. I think I am clear on the fact that the true 7.62 Nato chamber is a longer headspace than .308 and it is unsafe to shoot commercial .308 in a 7.62 chamber because of that, but ok the other way around? My question is if we ream with the 7.62 reamer but use .308 go/no-go gauges are we effectively still cutting the shorter headspaced .308 chamber? Since both cartridges headspace off the datum of the shoulder why are there not specific reloading dies for 7.62 Nato? This gun will never see anything but reloads from me so I can make them fit correctly but don't want to leave something behind to whoever that isn't safe with commercial .308. Any help to this would be appreciated.
 

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I would suggest that you stop worrying about the names, they are pretty much semantics. What you should be asking is how tight or how loose do you want the chamber in your rifle to be?

What is the intended use of the rifle? What bullet weights will you usually be shooting?

Some rifle chambers are cut on the tight side, for example Remington has a reputation for cutting tight chambers in the 700s. Other chambers may be somewhat looser, ie larger in diameter, longer throat, longer headspace, etc. but there is usually specific reason for this. For example, military chambers for 7.62 are usually looser because they want the chamber to tolerate some carbon and dirt and whatnot and still feed/extract reliably.

A tight chamber may be a bit better for accuracy, a looser chamber may be a bit better for reliability. But even that doesn't really come into play in a bolt gun.

So, why would you want a loose chamber in a bolt gun that will only see handloads? IMO there is no real reason to cut anything other than a SAAMI- spec .308 Win chamber in a bolt gun, and headspace it somewhere between the SAAMI go and no-go, 1.630" to 1.634".

Manson's 7.62 reamer may be sized to cut a slightly looser chamber than SAAMI specs, I don't know. They way to find out is to call Manson, they will happily send you prints of their reamer specs which you can compare to SAAMI .308, which can be downloaded directly from saami.org. While you have them on the phone, tell them what your preferred bullets are and they will tell you whether a specific reamer is best or less than best for those bullets, for example if you plan to shoot lots of Sierra 175 MKs they can tell you which reamer cuts the best throat for that bullet. Remember Manson does this for a living...

And the "308 is unsafe" thing is an urban myth. If the headspace is between 1.630" and 1.638" it's safe with .308 Win SAAMI spec ammo.

EDIT: I'm not Jon Wolfe, and I'll be interested to read his reply on this...
 

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I for some strange reason you decide to cut a 7.62 chamber for your bolt rifle, you will only be working your brass more.
There are many differences in the .308 - 7.62 chambers other than headspace. The 7.62 will create larger diameter main chamber area thereby making your .308 sizing die mash the brass down more every time you reload.
Please, for what you are intending, get a .308 reamer. You will be much happier in the end.
 

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Discussion Starter · #4 ·
You guys are very helpful. I am learning, but as usual it's the hard way :) For some reason I order stuff first then ask questions to find out just how dumb I can be. Hey in case anyone else needs one Manson has (this morning at least) new "7.62 Nato Solid Pilot Finisher with TiCN Coating" reamers for $60.00 :-(

Thanks very much for the help.
 

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What was/is the intended use for the above rifle? I personally would use a plain old .308 reamer before a NATO reamer.
 
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Discussion Starter · #6 ·
What was/is the intended use for the above rifle? I personally would use a plain old .308 reamer before a NATO reamer.
Ya that seems to be the consensus :) The very nice lady at Manson's ships super quickly so the reamer is already on its way and mine now! This gun will mostly be used for a heavy gun for cast bullet silhouette. Mostly shooting 200 grain cast to 500 meters. I get to do this at most twice a year so I figured since we are looking for a build project it was as good excuse as any. My friend with the shop that is going to put it together also has a range to shoot 500 yd. gongs likely with 150 to 168 jacketed. If I neck size and don't overwork the brass is there any reason it can't safely work? I had a couple case head ruptures last year with my M1a using fully processed LC cases. That is a whole different subject but it did teach me how unpleasant case failures can be. If I am inviting that again I want no part of it. Thanks Phil!
 
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Well as someone has said the NATO chamber has a generous body and a wide neck diameter, neither are conducive too accuracy or fired brass condition. At lease with the .308 Winchester reamer you get a much better body compared too the NATO.

If it were my project, I would seriously reconsider the NATO reamer and go with either the .308 Winchester or the M852 Match reamer. Both make great general purpose do everything well chambers.

Safety isn't the issue, that's a reloading and H/S issue. Using the NATO spec reamer will cause the brass too wear out sooner and the rifle will not be as accurate as it could have been for the same amount of money spent.

I would target my H/S for 1.634 not the very minimum.
 

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Discussion Starter · #8 ·
Thanks again for the explanations. I think I have my head around some of it now.
I know this comes up in one way or another often so I appreciate everyone's patience.
There is a ton of crap info out there about the subject so I was confused.
 

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We have all been there at one time or another.
I gave my younger son a couple of Fulton M14s with 7.62 chambers. He now sees why I hated that chamber. He is reloading and sizing is much harder if the brass was fired in a NATO chamber.
I may just have to stick a couple of new Bula barrels on them for him.
Good luck and have fun.

Semper Fi
Art
 

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Thanks again for the explanations. I think I have my head around some of it now.
I know this comes up in one way or another often so I appreciate everyone's patience.
There is a ton of crap info out there about the subject so I was confused.
I confuse myself all the time..... In a nut shell you want some room from the case mouth forward, not from the case mouth back.
 
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