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I know this has been asked a million times and there is a 1000 answers and everyone has there opinion but here is what I have.
I recently purchased a very nice older SAI rifle 40K range with all USGI parts.TRW barrel and bolt,rifle shows barely any use and the barrel is a 0 on both ends.
Now I stripped it down to clean and inspect and then disassembled the bolt to check the headspace. I used a set of Clymer 308 gauges to perform the check. Inserted the go guage and the bolt went all the way down without any restriction. Went to my NO GO gauge and it can close but I have to push down on the bolt to make it go home all the way. So then went to to field gauge and it will not close and there is a fair amount of opening between the lug and receiver.
Now from what I have gathered her on the forum and other sources, they say that the Clymer GO gauge is 1.632,the NO GO is 1.636 and the field is 1.640.If this is correct and I am assuming it is my headspace would fall somewhere between 1.636 and 1.640 correct. I have no other gauges so I did what others have said is a poor mans way of checking the HS.I got a piece of 3M scotch tape which I checked the thickness on my micrometer and it read .0015, so I stuck it on the NO GO gauge trimmed it around the shoulder and then rechecked my HS,The bolt would not go down.So if im correct and only assuming I take it my HS would be right in the 1.6375 range?
If I did my math correct and taking into the fact that I cleaned the chamber and the bolt as well as the gauge and those are the readings im coming up with is it safe to shoot both 308 and 7.62.
I don't reload and will most likely only be shooting good mil spec nato ammo in this rifle. What do you guys think and I know everyone has a opinion but i would like to hear from some of you on this. I feel from reading other posts and info that im OK?
 

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My Clymer NO GO is 1.634. You said you put the tape on the NO GO gage, which was already not closing. If you want to get a closer reading, put the tape on the GO gage and see if it will still close w/o any pressure.

You've probably already read it, but I go with what Gus says here: http://m14forum.com/gus-fisher/66601-little-bit-everything-do-headspace.html

There's a good explanation on the proper headspace to shoot both .308 and 7.62.

Edit, here's part of what Gus says:

"OK, so CAN a rifle be chambered so that both .308 Winchester and GOOD 7.62mm Nato Ammo be fired in it without problems? The good news is yes it can. Most factories who make or fully assemble their rifles chamber them so you CAN shoot both, but it is not absolutely certain in every rifle and with every type of 7.62mm Nato Ammo. Please see Number 2. above.

"Now, the GREAT thing is that if a rifle is chambered so that the bolt correctly closes on a 7.62mm GO gage at 1.6355" and does not close on either a 7.62mm NO GO gage of 1.6375" or the .308 Field Reject of 1.638" - then there are absolutely no worries about shooting either .308 nor 7.62mm in the rifle. This is how I chamber Garands and semi auto M14's for folks who want to shoot both .308 and 7.62mm surplus. (I chamber them so the bolt won't close around 1.635" to 1.636".)

"If you use .308 Winchester Headspace gages, exclusively, you can still chamber the rifle correctly for 7.62mm as well. You want the bolt to just close without friction on the NO GO gage. That will ensure you have the minimum for 7.62mm and not too much headspace for the .308 at 1.638"."
 

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The chamber headspace on your rifle is fine.

Using 'force' to close the bolt with the NOGO gage is wrong technique.
At the most, use of light fingertip pressure it all that should be used.

The IMPORTANT HS concern is that the bolt reliably rotates fully closed using whatever brand of 308W or 7.62 ammo.

When resizing cases for reloading you can do all the measuring you want, but make sure the bolt closes reliably!

Jay Kosta
Endwell NY USA
 
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