308 headspace vs 7.62

March 21, 2021, 10:35 AM

Hey all-

I know this is an old-type question but I haven't seen it come up here and I think this place is a deep well of wisdom and experience:

How much different is/should be the headspace for a 7.62 bolt gun (50's Israeli Mauser) vs a fresh 308 700 Remington?
They will each have their own brass and will not share.
Second question:
How long of a headspace is acceptable/safe on that old Mauser?

Bruce

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March 21, 2021, 03:31 PM

lyman

IIRC, in theory,
none,

however

the 7.62 gauges and the commercial .308 gauges measure from a slightly different datum point, I think,,

I have USGI 7.62 gages and a commercial set,
the numbers (headpace lenght) is different on each, (as in both go gages have different lengths or measurement etched in them,)

I've dropped both in a M1A and the gun passed with each, (and showed roughly the same 'measurement' as in how much the bolt had left to close etc)

eta the mauser will have a more 'generous' throat and likely chamber as well

March 22, 2021, 01:27 AM

RNshooter

"eta the mauser will have a more 'generous' throat and likely chamber as well"

Can we define "more generous" for someone that isn't sure how many thousandths that might be between "okay" and "no way"?

Bruce

March 22, 2021, 05:32 AM

PHC

My advice is to purchase a good case gauge, I use gauges made by Dillon, if the shell passes, use it if not put it in the scrap bucket. Easy peasy, no sense trying to make a big deal out of it.

March 22, 2021, 06:28 AM

RNshooter

I have the RCBS precision mic for 308. No "pass" or "fail", just very precise measurements.

Bruce

March 24, 2021, 09:00 AM

lyman

quote:
Originally posted by RNshooter:
"eta the mauser will have a more 'generous' throat and likely chamber as well"

Can we define "more generous" for someone that isn't sure how many thousandths that might be between "okay" and "no way"?

Bruce

aenerous as in not a match chamber, ,
chamber diameter is not measured by head space,
neither is the throat,

remember, the rifles were made to work in all conditions, so they will not have a tight match type chamber,

as PHC mentioned, get a case gauge, dillon or wilson are fine, I have both,

and if you are worried about the throat, there are ways to measure that as well,

I use a bench rest die for 223 that I used for my service rifle ammo, very precise measurements for OAL, which you may or may not need for the MAuser

remember , headspace is the distance from the bolt head to the datum point on the shoulder for .308/7.62

re the Rem, it will likely have a more precise chamber, and likely a shorter throat, (meaning OAL will likely be slightly different depending on the bullet selected to reload

March 24, 2021, 09:01 AM

lyman

quote:
How long of a headspace is acceptable/safe on that old Mauser?

BTW, to answer this question,

the mauser should pass the Field gage,

June 02, 2021, 12:05 PM

2tonicP220

quote:
Originally posted by RNshooter:
Hey all-

I know this is an old-type question but I haven't seen it come up here and I think this place is a deep well of wisdom and experience:

How much different is/should be the headspace for a 7.62 bolt gun (50's Israeli Mauser) vs a fresh 308 700 Remington?
They will each have their own brass and will not share.
Second question:
How long of a headspace is acceptable/safe on that old Mauser?

Bruce

My FN made Israeli Mauser had what seemed a 'tight' 7.62 chamber... Cases were not stretched or had any weird bulges. My Argentine FN49 had what I consider a generous chamber, but headspace was fine. Now my Isapore 2A in 7.62... Very swollen cases, esp toward one side and stretched. Sure was not made for reloading.

As for what denotes 'generous', this photo says it all. Same ammo but L. fired in a 7.62 chamber, R. in a .308 rifle. Thank goodness about all 7.62 brass you will run into is extra thick in the web, and weighs a lot more. Heaviest brass I ever weighed was Brazilian CBC 7.62... It was many, many grains heavier than .308, and a lot more than a most 7.62 brass.

June 02, 2021, 12:21 PM

RNshooter

My Mauser seems to have a normal chamber. It would not even come close to closing the bolt on a 7.62 max gauge.

Bruce