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I have a question for anyone who might be able to assist.

I enjoy shooting the M1A chambered in 7.62 nato. Now I'm in the process of starting to do my own reloading, however, there is a distinct difference between the .308 WIN and 7.62 Nato round. My question is, 1) the manual I have lists the .308 information as being the same for the 7.62 Nato, but my understanding is that that there is a significant headspace difference. That being the case is there anyone who manufactures dies for the 7.62 Nato round specifically, or is it possible to use the dies for the .308 safely and effectively? 2) If there are 7.62 Nato dies, where can I find them?
 

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As far as I know... the only difference I have ever seen w/ 7.62nato and 308 win is that the 7.62nato brass has less internal volume than the average 308.... I really wouldn't worry about it... I have loaded winchester whitebox 7.62 brass w/ the same reciepe that I did in my hornady match brass and had no issue...

This is like the 223/ 5.56 argument, I have shot, my friends have shot, 223 and 5.56 through their guns and other guns that are stamped .223, 5.56, .223 and 5.56, and never once had any issue what so ever... its like calling 30-06 7.62x63 or 300win mag 7.62x67


MIke.
 

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It is not the same as the .223/5.56mm issue.

Use .308 Winchester data for .308 Winchester cases. Reduce 5% for 7.62mm NATO cases and rework up to make sure you do not have excessive pressures. This assumes you have a chronograph.
 

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The difference is in the throat mainly. The dies for the 308 are the same as for the 7.62. Rounds for my M1A get full length sized, for the bolt gun get neck sized only. For the auto loader I started low, found the level that it operated the action reliably, then tuned it for accuracy. I crimp all the M1A rounds.

The same thing applies to 223/5.56. Remember that military brass is thicker than commercial with less internal volume. Pressures run higher in them for a given powder charge. Hence they are reduced 5% as a rule.
A chrongraph is very helpful but not completely necessary.

Don
 

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Guster,

Welcome to the forum. Rules are to join in and have fun and be polite.

You may have noticed that 7.62×51 surplus ball ammo is sold to anyone who has a .308? That's because the new cases for either chambering have the same outside dimensions and the NATO ball bullet shape will fit either commercial or military freebore lengths. That's why you don't see separate dies available. The dies are the same because the sized cases are the same, though if you have a semi-auto gun that stretches cases a lot or doesn't feed easily, you can also get what is called a .308 small base die for sizing the cases an extra couple of thousandths.

A tool called a GO gauge is used to set chamber headspace. The NATO 7.62×51 GO gauge is 1.6350" while the SAAMI .308 Winchester GO gauge is 1.6300". That extra five thousandths in the 7.62 GO gauge is for reliable full auto feed. Contrary to what you might suppose, the SAAMI .308 Winchester specification allows a 0.004" interference fit between a new case and the chamber. The chamber headspace specification is 1.6300"+0.0040", while the case specification is 1.6340" -0.0070".

Most people aren't aware that chambering a round can easily shorten a cartridge case as long as the chamber is wider than the case. Hatcher measured up to 0.009" (IIRC) shoulder setback from rapid chambering in the Enfield, for example. A manually operated bolt has a lot of camming leverage, so it easily squeezes the case to fatten up and fill out the clearance in the chamber diameter. That makes for very good bullet centering when it happens, which is why match shooters find a SAAMI minimum chamber is often more accurate than a looser one.

NATO arms designers apparently wanted nothing to do with possible interference fit in full auto gear, so they just made their chamber specification longer than the SAAMI maximum new case dimension, then kept the same spec for new cases that SAAMI has. (By the way, I have an old SAAMI drawing that allows the chamber to have a couple thousandths more length than the current FIELD GO gauges do, so this spec has apparently changed over time.)

The only other difference in headspace is that the NATO FIELD NO GO gauge that tells them when to retire a barrel is 1.6455", where the SAAMI FIELD NO GO is currently 1.6380". I don't know if that extra 0.0075" reflects the fact military accuracy requirements are lower than many civilians want, or that the military is always firing new cases built to a standard with thicker brass and a hardness that withstands full auto and will stretch quite a bit in a very long chamber without head separation? Indeed, between the World Wars, Hatcher describes how they segregated brass annealed softer for full auto from harder brass they labeled "rifle".


308 Winchester (SAAMI) Gauges

GO - 1.6300"
NOGO - 1.6340"
FIELD - 1.6380"

Shop (Military) Gauges

GO - 1.6350"
NOGO - 1.6405"
FIELD - 1.6455"


The matter of the freebore leading into the throat is the other main NATO chamber difference. It is 0.090" is the standard SAAMI chamber, and something more like three or four millimeters in the 7.62, IIRC? I don't have a hard number handy, but the longer throat is for military specialty ammunition with short ogives that would jam in the SAAMI throat. The longer freebore lowers the pressure of a round as compared to what it would develop in a SAAMI chamber, which may partly account for some surplus loads being too warm?

That brings up the last issue that needs to be touched on: chamber pressure spec difference. There is a lot of wrong information in print on the web on this point. Indeed, most of it. You repeatedly see the NATO spec is 50,000 psi max, while the SAAMI spec is 62,000 psi max, making it appear SAAMI compliant ammo is unsafe in NATO guns. Not so:

The problem is the military continued the pre-war practice of reporting copper crusher test results as "psi" instead of "cup" up into the 1990's. Thus, the commonly quoted 50,000 psi military spec is actually 50,000 cup, and is for ball ammo, while M993 AP is specified at 55,114 cup (matching 3800 bar by copper crusher used originally by the European NATO countries for that round). These should be compared to the old SAAMI spec of 52,000 cup, also measured in a copper crusher, and not to the new 62,000 psi spec, which is measured by piezo transducer. The bottom line is, the NATO 50,000-55,115 cup pressure limits neatly bracket the SAAMI spec measured in cup. They are, for all practical purposes, the same pressure spec.

Caution needs to be taken with surplus ammo. Remember it is surplussed out for a reason, and excess pressure has shown up in some military surplus. I guess the governments don't worry about being sued.

You can read more detail about the pressure issue by Firing Line forum member, FALPhil, here.

Bottom line: use .308 dies for reloading. Work your loads up separately for each case brand you have, as they vary quite a bit in the .308.
 

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I was told to use NATO primers only in the military style semi auto rifles from an online reloading course that I took do to the chance of a slam fire. Other peaple on some of the forums that I belong to disagree with this information but I have heard of several instances and have sean slam fires on youtube. I will always use the Nato primers for my M1a's and M21 and hope that every one around me shooting does the same . BE SAFE AND ALWAYS HAVE FUN!!!
 

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For a long time NATO style primers were not readily available to the general public, meaning they weren't carried by normal vendors. During that time, Federal primers got a reputation for being too sensitive because most slam fires at matches occurred with them. Some years ago, Federal published a refutation of this in Precision Shooting magazine, pointing out that more match shooters used Federal primers than any other, so it was only natural to expect most random slam fires would occur with them. They had no indication the number of slamfires per round loaded were any greater with their primers than with any other, and, indeed, a lot of Federal match ammunition has been put through M14 variants and maintained a good reputation.

Nonetheless, these days CCI markets the #34 (large rifle) and #41 (small rifle) military hard primers. Like military primers, these are magnum primers, which helps ensure cold weather ignition. You can buy these primers (when they are available) and use them for extra insurance, if you choose to.

Most slamfires seem to occur because of high primers. One fellow pointed out that some brands of commercial brass have less deep primer pockets than military brass, and that may exacerbate the problem. He recommended owning a primer pocket depth uniforming tool and using it in all cases, including military, to clean the primer pockets after every firing. That way, as the brass in the web is pushed back with repeat firings, primer pocket depth is maintained.

You also need to learn to feel seated primers with your finger to tell if they are properly below flush with the case head. Seating primers very firmly, rather than with a delicate touch, helps. The only commercial priming tool I've seen that guarantees the primer sits at least 0.004" below flush with the case head is the one built into the Forster Co-ax press. They also make a bench priming tool the call a Co-ax priming tool, but it does not seat to a guaranteed depth the way the one on the press does. That's one reason I like the Co-ax press for loading 7.62×51 and .30-06 for the Garand.

A second cause of slamfires is out-of-spec guns. Check that your firing pin protrusion is within spec and replace it if it isn't. Check the receiver safety bridge isn't bent. Check that your bolt is within spec. Some idiots cut the ears of the hammers at one time, so be sure you didn't get one of those hammers. If this stuff isn't familiar, take your M1 Garand or M14 or M1A out of its stock, snap the trigger group back in place and operate the bolt manually while you look up under the back of the receiver so you can watch the hook on the back of the firing pin and see how the firing pin is blocked?

Another cause of slamfires is not really a slamfire, though the shooter can't tell the difference. Rather, it is hammer following. This where bolt closing jars the hammer off the trigger hooks and it strikes the firing pin. It is usually caused by worn trigger group parts. Make sure your mainspring is strong enough. Make sure your trigger group pin holes are not worn open or oblong. Make sure you can't wiggle the trigger enough to make the hammer come off the hooks and make sure that the sear comes to the rear hooks far enough in advance of the front hooks letting go.
 

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I shoot Sierra 168 grain Match Kings in G.I. 7.62 NATO cases, I use IMR 4895 or IMR 4064 as the powder and Match Large Rifle Primers.

You should take any information from loading manual, back the load off at least 5% and find a load that works for you and your rifle.

I used to shoot a near perfect score for the Army and the Marines with my first M1A, these days, my vision is not what it used to be, so I am happy shooting expert or taking out a coyote a 300 yards.

Jerry
 

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Great info here. I just purchased 1,500rds of once fired 308 military brass with crimped primers. I knew the cases were thicker and heavier and now i know i need to cut back on the powder charge too. I been also thinking of using the thicker brass in my fluted chamber Cetme.

I reload for all my military semi auto's using the CCI #34 nato primers and the IMR 4895 powder its the correct burn rate for the military semi auto cycle timing.

I even reload for all my military bolt actions using the same CCI #34 nato primers and the IMR 4895 powder too this way i won't mix up and use the wrong ammo in my semi auto's. Besafe do it right.
 

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BigBill if you do not have a swedger you may look in to getting one. swedging the primer pockets realy helps to reprime. I use the Dillon swedger but there are other brands out there. Always have fun.
 

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Look into a RCBS small base X-die for your sizing. Won't have to trim the cases as much, and I think that the small base design is smart for a M1A. I also use the CCI #34s.
 

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Hello gents,

Forster makes NATO spec headspace gages for 7.62 and 5.56, but does anybody know if someone makes NATO spec case gages? For me, one part is knowing I have a good chamber, and the other part is knowing I have created good ammo. I have a really nice LRB M1A and about 4,000 rounds of once-fired (from bolt guns) Black Hills Match brass and I am just dying to reload, but I'm scared to death of my wife were I to ruin my gun by being dumb--it cost a lot, and required some innovative reasons why I "needed" it!

I have a Dillon 550 press, and plan on using either a Forster or RCBS bushing die for re-sizing, a primer pocket uniformer, a Forster primer seating doo-dad, and MILSPEC CCI No. 34 and No. 41 primers for my M1A and AR 15, respectively.

I know there are SAAMI spec case gages, but at this point I do not trust them with respect to making sure my ammo is right for my NATO spec chamber; for me, "good enough" isn't, unless someone can convince me.

Thanks, I appreciate any info anyone would be kind enough to share.

J
 

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I also have a Dillon 550 and have reloaded a couple thousand 308 nato for my M1A's . I have had no miss fires and no damage to my rifles. as long as you go by the book you should have no problems. I beat my self up about am I doing every thing right. I alway question my self about every step. I guess I am saying that you can never be to careful. My M21 cost me almost $4000 and a two year wait. So I know how you want do it right. I do not think if you follow the books that you will have a head space problem. Check and Trim your cases after every fireing and you will be fine. I use the GTC trimmer it makes the job easy simple and fast with match quality every time. Good luck out there and have fun reloading and shooting.
 

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The NATO headspace is longer so a SAAMI-spec case will go in the chamber. At that point you have two issues to consider: bullet seating depth, and brass that is sized too small.

Max bullet seating depth is easily established for your gun and then all you have to do is ensure that your reloads with that bullet are shorter than the max length, as far as reliable chambering goes. Worst thing that would happen is not being able to close the bolt. That may be inconvenient but won't hurt the gun, anyway. Just make up some dummy rounds and seat the bullet a quarter turn on the seater stem each time till they chamber. Easy enough.

As far as sizing the brass too much, it wears out the brass sooner and then you risk a head separation. Shouldn't be a destructive event but you don't want to do it if you can avoid it. My preference is a tool like the RCBS Precision Mic which lets you measure the shoulder setback when the case is resized. After the brass is fired in your gun, use the tool to measure the shoulder position, then set the sizing die to push it back only a few thousandths. My goal is 0.002" shorter than the chamber for bolt guns. In a semi-auto you may wish for a little more clearance? I don't reload for any semi-auto rifles so others may have better insight.

The above, plus normal caution working up load data, should serve you well.
 

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If you go back and read my first post, you will see why new cases are the same size for both .308 and 7.62×51 NATO. The extra NATO chamber length is to prevent the interference fit SAAMI specs allow. So, the same case gauge is applicable for both chamberings.
 

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I also have a Dillon 550 and have reloaded a couple thousand 308 nato for my M1A's...as long as you go by the book you should have no problems...I do not think if you follow the books that you will have a head space problem. Check and Trim your cases after every fireing and you will be fine. I use the GTC trimmer it makes the job easy simple and fast with match quality every time. Good luck out there and have fun reloading and shooting.


I guess that's the thing that's killing me right now is not being sure how to make sure my brass is re-sized correctly. unclenick put out some good information about dimensions of the different chambers; so, if my newly reloaded ammo rests correctly in the .308 Win case gage, I should be alright?
 

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Yes, and the ultimate test is to chamber them in your rifle. My added comments re: the RCBS Precision Mic were more along the lines for longevity of your reloaded brass, and not a requirement.
 

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I use RCBS small base dies and both 308 and 7.62 nato brass in my 7.62 nato chamber. Different loads for each type of brass. In my nato chamber they are tight but shoot excellent. Work up new loads for your rifle the same as you would normally. I do not shoot a M1A but a DPMS LR AP4 ish home built rifle with a 7.62 nato chamber.

AL
 

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Discussion Starter #20
Wow! Great info here. Thanks all for the input. Now to get started with handloading. I look forward to seeing improved groupings with my M1A, Garand, and M1917 with handloads.
 
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