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Discussion Starter · #1 ·
On the surface the question about: "Why know your head space number, it's useless".. seems to be a good one, just buy NATO cert. or US commercial ammunition and forget about the head space.. An answer may be: Not many owners do that, they come into other ammunition at a bargain price and buy it to shoot. some also reload..

The safety factor, for both shooter and weapon is the primary concern, for me anyway.. The cartridge case head space can be measured, , there are several Cartridge HS gauges available, I like the RCBS model. It is a good tool to compare various types/brands of ammunition,, including resized cases of all brands.. The Cartridge case HS numbers are useless unless you know the HS number in your rifle..

The M1 and M14 type rifles come in a spread of chamber numbers, 1.629" up to and beyond 1.638", maybe others.. Always keep in mind the head space of your rifle when the chamber is clean and unfired is not the same HS number as it will be after you start to shoot.. The chamber gets shorter and tighter from heat and carbon..

If you accept the above,than it is in your interest to use ammunition that has a Case HS number at least .003' to .007" smaller the a cold clean chamber HS number..

As an example: I took samples of case head space readings off one of the most popular USA ammunition makers, one of the most accurate also,, Win. 308 ammunition.. Win. 308 chambers have as a goal a HS number of 1.630", this may be only my opinion, but shared by many. The ammunition mentioned has a case HS number averaging 1.626", that will indicated how changing chambers number during use is overcome..

Personal resizing cases, I set the case shoulder back a Mim. of .005" under the chamber head space number.. Art
 

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Head space and case body size

Art,I worked on a couple rifles and the owner thought it was a head space issue. Took both rifles apart and checked head space with go,no go and field gauges. Then took loaded rounds Nato 7.62,LC Natch,Federal Match and my hand load to check. This was all done with the bolt disassembled for safety reasons and so there was no interference from extractor&ejector. After checking then used the owners reloads and found the problem. It was the body of the case from not being small base sized. The brass was out of a belt fed which has a generous chamber for fouling and heat. The mentors that have graciously helped me said head space gauges are a must to determine if you are in SAMI specs. There seems to be confusion on 7.62 and 308 on head space. The company I brought my reamer from said head space is the same,but its the case body is where difference lies. This I found out checking the two rifles out and calling reamer company for a drawing of dimensions of 7.62 and 308. Returned to two rifles and told the owner it was his reloads that he needed to use a small base die on that LC brass out of a belt fed. Once again, once fired brass is not ALL EQUAL once fired brass. Need to know what it was run through. Always look a gift horse in the mouth(brass included).
Pfc out
 

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First of all, I am not any sort of expert on M-14 rifles or headspace. That being said, in over fifty years of shooting M-1's and M-14's, I have never heard of any serious problem caused by excessive headspace. I have seen lots of problems and damaged rifles caused by reloaded ammunition. I have fired an M-14 that would swallow a Field guage whole. It functioned perfectly on semi and full auto. If you wish to worry over your rifle, you should obsess over the ammo you feed it. Just my experience. Regards, Clark
 

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Discussion Starter · #5 ·
Good Infomation here..

That is a great read, hope everyone read it and puts it in the bank..

There is no reason not to use Small base dies all the time, case life is limited in the M1A, plus there is strong evidence here that improved accuracy results using SB dies.

Thank you for adding this material.. Art
 

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Thanks for the information!
 

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The company I brought my reamer from said head space is the same,but its the case body is where difference lies. This I found out checking the two rifles out and calling reamer company for a drawing of dimensions of 7.62 and 308. Returned to two rifles and told the owner it was his reloads that he needed to use a small base die on that LC brass out of a belt fed. Once again, once fired brass is not ALL EQUAL once fired brass. Need to know what it was run through. Always look a gift horse in the mouth(brass included).
Pfc out
Those Old Service Rifle shooters know a few tricks about prepping brass. This was passed on too me many years ago I've used it and it works so well, I've passed it on a few times myself.

All brass has some spring back after it sized, MG fired brass is pretty bloated so after resizing it springs back more than it should. Before you get started prepping your brass in your .308 resizer run them through a striped FL 30.06 resizer first this works the brass down near the case head only, where its needed most with once fire MG brass. This doesn't touch the case anywhere else so your not depriming or bumping the shoulder back at the same time.

After you have prepped your MG fired brass you can resized them in your std die set, working MG brass down in increment's like this really cuts down on brass spring back too almost nil. Another pleasant side effect is the brass is also much easier too resize, it takes a lot less effort.
 
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