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Hi,

Have found just found this forum and have a question about the new M1A my son just bought. It came with a notation of the headspace being set at 1.631. To me this size is most suitable for the .308 Win round due to the required headspace for the .308 WIN round and that of the 7.62 Nato round being larger.
Has anyone made a determination due to headspace on which round to use in the newer Springfield Armories' M1A's? Your thoughts?

Thanks, James
 

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First off, welcome from CT.
Plenty of SAI users aboard.
I have shot everything in mine. What the tag reads and the actual headspace are not necessarily the same. I suggest checking your chamber to get the dimensions. 1.631 would be considered tight for surplus but a lot of it has been burned up in them.
 

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The M1A is a commercial rifle and uses chamber headspace that is SAAMI spec for .308 Winchester. Some early M1A rifles used USGI M14 barrels and had slightly longer headspace, at the low end of 7.62 NATO.

Some surplus 7.62 NATO ammunition from foreign countries might be too large for the M1A. It usually comes from countries that don't readily use .308 Winchester commercial firearms.
 

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Head space sometimes gets over thought.
In a basic senses if the chamber is cut with in spec and the ammo is with in spec the rifle should function.
As far as I can tell 308 win and 7.62 NATO CARTRIDGE HS are the same
SAAMI
Cartridge headspace is max 1.634” min 1.627”
Chamber
Max 1.640” min 1.630”

NATO
Case
Max 1.634” - 006”
Chamber
Min 1.6355” max 1.6405”

The chambers are different and there might be a few other case differences but honestly
Not enough to really matter , but I’m just a novice.

I’m not so sure if there is any 308 you can buy that will not have over pressure issues at the gas port?

So I’m my small head even if you take a minimum spec chamber and a max spec case
and cycle it through the loading process of the rifle should “resize” the case in the chamber.

Now this all relies on manufactures being very close to using the same data lines or dat point and so on.
My 308 M1 garand is cut to SAAMI min specs and has eaten all the 7.62 M80 ammo I have shot through it with out issue other than poor accuracy.

Good thing there are pros here that can offer more detail and have access to better data , drawings, tech manuals and such.

I will be cutting my M1a build very close to min chamber specs . As close as I can anyway with a pull through reamer
 

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Typically, USGI 7.62 ammo will fit and work fine in a 308Win chamber.
'Some' foreign 7.62 is encountered that is too large (long headspace) for 308Win chamber.

I'd avoid buying large quantities of 7.62 ammo (except USGI) until you verify that they will chamber easily in the rifle. Attempt to chamber a round and then LOOK to SEE that the bolt has CLOSED completely. The bolt should also be easy to open with an UNFIRED round chambered - a moderate pull on the oprod should be enough, if it's stuck tight, then the bolt has jammed the round in the chamber - not good.

Jay
 

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Welcome from SE GA.

Check out TonyBen's cleaning and maintenance videos for the M14.
 

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I just built a Brit/Ausi L1A1 on a Coonan inch receiver and head-spaced it to commercial standards with Clymer .308 go/no go gauges. Works fine with any ball ammo I have on hand. That includes old Samson .308(IMI)...Norinco steel case .308...Portuguese M80 nato spec...Lake City match ammo(172gr I think)...new Federal XM80.


I had checked all the above ammo in the L1A1 and all is/was easily chambered and fired from the home built SLR and I set the headspace fairly snug to the 'go' guage
 
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