.308 Win. Vs 7.62 X 51 NATO

[Jim]

I've been told by some that the dimensions of the two cartridges are the same and some say they're different. I've been through all my books and cannot find anything that shows a difference in dimensions.

What say the court?

[felix]

Talking about new cases or chambers? Military chambers are looser. Any once fired case should work. Not so the other way around. A closely spec-ed chamber will not accept stretched out cases from these military chambers. The converted 303 British guns to 308 have really long chambers, and their ammo is indeed soft in the shoulder and does, via experience, take a lot of force to bring back into line. I keep the cases separate nowadays. ... felix

[Jim]

That explains it. Thanks, Felix.

[spqrzilla]

The problem with 7.62x51 NATO versus .308 Winchester is that their pressure specifications are done using different measurement protocols. Further, old military specifications date back to the transition between CUP and PSI measurements, and the specs can read as "PSI" when they are in fact expressing CUP. The military specification also has different statistical measures regarding sampling and allowable variation from SAAMI specifications. As a result, it can appear that .308 Winchester pressure specifications are higher than 7.62x51 NATO ( which is why you will sometimes see recommendations not to use commercial .308 Win in military rifles chambered for 7.62 x 51 NATO - the opposite of the situation with 5.56mm NATO versus .223 Remington ).

It is my opinion that the differences in practice are just not there. That within manufacturing tolerances that the pressures of the two specifications are functionally similar.

However, this can create a huge amount of internet discussion.

[sqlbullet]

My understanding....External dimensions are the same (cartridge), but the chamber dimensions and the pressures are not.

This is the right rule:

7.62 in 308 is fine, but not the other way. In other words, if your gun is marked 308, shoot either one. If it is marked 7.62, shoot only 7.62.

PDF with details here (http://www.surplusrifle.com/shooting2006/308vs762nato/pdf/308vs762nato.pdf).


There are headspace differences between the two rounds. The .308 go-gauge is 1.6300, the .308 no go-gauge is 1.6340. The 7.62 go-gauge is 1.6350, the 7.62 no go-gauge is 1.6405. Since NATO military ammunition can come from any NATO country, and the goal is the ability to interchange ammunition, the military chamber is larger.

[Larry Gibson]

My understanding....External dimensions are the same (cartridge), but the chamber dimensions and the pressures are not.

This is the right rule:

7.62 in 308 is fine, but not the other way. In other words, if your gun is marked 308, shoot either one. If it is marked 7.62, shoot only 7.62.

PDF with details here (http://www.surplusrifle.com/shooting2006/308vs762nato/pdf/308vs762nato.pdf).

Going to have to disagree with the "right rule". I've measured the psi of enough US and foreign made 7.62 NATO and commercial .308W to note that that is not the rule. There isn't any rule. The pressures over lap with some 7.62 NATO having psi's as high as any .308W and visa versa. That PSF article, like most, confuses CUP psi's with peizo electrinic psi's. It also confuses the PMAPs as "working" pressures which they are not.

The cartridges are essentially the same. However one should consider that 7.62 NATO cartridges are designed to function in gas guns. Some .308W commercial ammuntion is designed for manually operated systems not gas operated systems. That is the only difference. If you think there is any difference in psi between M118 SB, M118 WB, M118 LR, Numerous lots of M80, M61, M59 and M62 then you'd better invest in some pressure measuring equipment and quit depending on internet "reports" that use erroneous information to draw erroneous conclusions.

Just a quick example of a recent test with the same rifle, same day, same conditions;
Winchester factory 150 PP, 55,500 psi(M43)
Remington factory 150 Core Lokt, 55,700 psi(M43)
US M118 SB LC88, 55,700 psi(M43)
US M80 LC74, 59500 psi(M43)
US M80 WRA69, 60,400 psi(M43)
US M80 LC87, 64800 psi(M43) (yikes!!!)
Canadian M80 IVI70, 58,000 psi(M43)
Cavim M80 91, 53100 psi(M43)
Indian M80 OFV82, 42,600 psi(M43)
Malasion M80 MAL11-83, 52,200 psi(M43)

All measured velocities were also reflective of the measured psi; the higher the psi the higher the velocity. Standard SAAMI testing proceedures were followed. Test rifle was with a new 10" twist barrel (less than 800 test rounds through it) with chamber cut to minimu dimensions and headspace. PSI and velocity testing done with an Oehler M43.

That was only a recent test of actual pressure measurements (not based on supposed "working" pressures of guestimations such as QuickLoad) and I have many others that show it is a c**p shoot with any 7.62 NATO spec ammuntion vs .308W commercial (Rem, Win, Federal and Hornady) as far as which has the higher psi.

Like I said.....ain't no "rule".

Larry Gibson

[swheeler]

"Cavim M80 91, 5311 psi(M43)"

My goodness Larry I'm surprised the bullet made it out the muzzle, talk about LOW pressure! wink-wink

[longbow]

I don't know how many times I have seen this discussion and just about every time it is different.

My understanding is that .308 was/is dimensionally interchangeable with 7.62 x 51 and that it was/is the same cartridge loaded for sporting purposes. I have seen arguments that they are not even dimensionally interchangeable though.

My "Cartridges of the World" 3rd ed 1976 states that "...the .308 is nothing more than the U.S. T-65 or the Nato 7.62 x 51mm military round."

So, after reading several articles on just how different these two cartridges are I decided that maybe an ammunition manufacturer could tell me for sure so I contacted Remington and Winchester.

Here are their responses:

Remington:

"Thank you for contacting Remington Arms. I'm not sure what you are referring to with T65. However, the 7.62x51 and the NATO rounds are the same. The .308 and 7.62 have the same cartridge size and the military chambers are oversized like you mentioned. That said, we do not recommend shooting 7.62 in a sporting .308. The 7.62 ammo is contracted out (in many cases outside of the US) and does not have to follow SAMMI specifications. There is a common problem with excessive pressures with this ammo and that's why the military chambers are oversized. The .308 is not oversized and that's why it's best not to shoot NATO rounds in it."

Winchester:

"Information I have indicates the T-65 or 7.62Nato is interchangeable with the .308W cartridge. Personally have never had a problem firing 7.62 Nato in a variety of .308W chambered rifles."

So, they are the same but may not follow the same rules for loads and pressures.

Me, I'm not worried about it.

Longbow

[Jim]

So, is this rifle rated for milsurp ammo?
http://fgsp.files.wordpress.com/2011/04/photos-0062-e1302746124144.jpg

[spqrzilla]

sqlbullet, that article is an example of what I was talking about. The pressure differences that Trope refers to come from a confusion between CUP and PSI, where the old military specs read "PSI" when in fact they were referencing CUP pressure numbers. I think Trope exaggerates the pressure differences as Larry Gibson mentions.

longbow, I think the Remington response you quote is confused.

Jim, yes, that rifle is chambered for 7.62x51mm military ammo.

[AaronJ]

My stepdad gave me a Reminton 700 in 308 as a birthday gift when I turned 16. Along with the rifle he gave me 200 rounds of surplus 7.62X51. After shooting a few boxes of factory ammo I tried the surplus stuff. Almost every round fired resulted in the bolt having to be tapped open. I gave the rest of the surplus away and have stuck to only 308 for the rifle ever since.

On the other hand my HK 91 was clearly marked 7.62 and was very happy when feed large amounts of it.

[felix]

Jim, just make sure that gun does not use machine gun ammo. Look for the NATO sign, and the odds are good that the ammo is NOT machine gun grade. Not only because of the long chamber that gun MIGHT have, and likely it does, but also because of the weakness that particular action has. I would keep the ammo around 45K cup as max, like what the Indian NATO 308s appear to have by my shooting. ... felix

[docone31]

Jim, I have several through the years. I have two now.
With castings you will have no issues there, with paper patching the same.
I have not had issues with MilSurp ammo, surplus ammo, or factory ammo.
I have not loaded hot, so I have had no issues, pressure signs, etc.
A great rifle, my wife loves hers. I put reciever sights on ours rather than scopes. I plan on an Huber trigger down the road.
A great rifle. Once bedded down, an accurate rifle also.
My rule for ours,
As long as it is reasonable, I am not worried. Hot loads are wasted on me anyway.

[sqlbullet]

Larry, the rule I stated is not with regard to pressure. Nothing to do with pressure. It is with regard to safety of the cartridge in a given chamber.

As you point out in your post, your chamber was cut to minimum dimensions. It therefor fully supported the shoulder of the cartridge and prevented case stretch and possible head separation.

The point of my rule is exactly that. 308 chambers are cut to smaller dimensions than 7.62 chambers. And, 308 brass may be thinner than 7.62 brass. Combine a generous chamber (7.62) with possibly thinner brass (308) and you have a recipe for a potential head separation.

Hence, the rule is not about function or pressure, it is about ensuring the chamber will do it's part in preventing a head separation.

Full disclosure: I do not currently, nor have I owned either a 308 or a 7.62 rifle. I am conveying book learning only.

[Larry Gibson]

"Cavim M80 91, 5311 psi(M43)"

My goodness Larry I'm surprised the bullet made it out the muzzle, talk about LOW pressure! wink-wink

I have found quite a few of the foreign made 7.62 Cartridges to be of low psi and velocity. Further study invariably turns up smaller statured men in the army and FN-FALs for rifles. Many such cartridges do not have the NATO "+" on them as they obviously do not meet NATO specs.

BTW; I have never found any reference (documented) that supports "machine gun" 7.62 NATO ammuntion was of any higher psi. I have documentation (US) where linked machine gun ammunition was of the same psi specs as all other 7.62 NATO cartridges of the same type (ball, tracer, AP, etc.). Some is marked as "For Machineguns Only" because it did not meet accuracy standards for rifles or was to be used for overhead fire. Otherwise the ammo is the same and is compatable with rifles.

Larry Gibson

[Larry Gibson]

sqlbullet

My opologies if i misunderstood but you did mention pressures; "My understanding....External dimensions are the same (cartridge), but the chamber dimensions and the pressures are not."

With regards to dimensions the external dimensions are the same between 7.62 NATO and the .308W. I don't think you are going to find any "7.62 NATO" loading dies. They are either .308W dies or occasionally list the same dies for both cartridges. As mentioned most commercial cases are thinner in the web area. This posed some concerns about case head seperation on initial firing in milspec chambers (milspec chamber dimensions are more generous than SAAMI dimensions). However, this has proven not to be the case (pun intended) . Many users of 7.62 rifles use Rem, Fed, PMC and even some Win cases. Also many who load for the M1A with milspec chambers know that one usually gets case head seperation in 4-6 firings. I had numerous case head seperations with LC, WRA, RA and M118 cases before I figures all this out back in the early '70s. I mean complete case head seperations BTW where the case head was ejected and the case body remained in the chamber. Nothing bad happened to the rifle or me. Most everyone else had the same thing and that's why many only fire cases 4-5 times at most (RCBS X-dies solve this and give 16-20 firings per case).

Been to Alaska numerous times on military ops and carried an M14 with factory Winchester 180 gr PPs for bear protection. Fired lots of that factory ammo without a single case head speration. many others have also. Not saying I make it a practice to use WW cases but I know many who do. I understand the warnings and SA used to specifically warn against using WW ammo but now just warn against all handloads. A friend of mine had case head seperations with WW cases in a FN-FAL on the first reload firing but was using small base dies. Switching to Forster Benchrest dies, adjusting the sizing to match the chamber headspace and he got the usual 4 firings.

I appreciate the concern about safety. If one is not familiar about loading for 7.62 gas guns then one best stick with milsurp cases. However, with regular dies and regular FL sizing incipieant case head seperation will still occur after several firings. Is it any "safer" if case head seperation occurs on the first load or the 4th or 6th? Best of avaiod case head seperation all together, eh?

Larry Gibson

[Jim]

TECHNICAL MANUAL 43-0001-27
US ARMY AMMUNITION DATA
JUNE 1981

I have no idea if this information is out of date or not. Every cartridge type listed for the caliber shows a chamber pressure of 50,000 PSI.
http://fgsp.files.wordpress.com/2011/04/photos6-e1302803693328.jpg

[spqrzilla]

Probably actually CUP. Just as an example, go look at Hodgdon's reloading data for .308 Winchester and note how often a .308 Win load for a 150 grain bullet that is in a medium speed powder and is doing about 2750 is at 50,000 CUP.

Here's an example:
150 GR. NOS BT Hodgdon H4895 .308" 2.800" 43.0 2742 43,200 CUP 45.5 2870 51,000 CUP

[Harter66]

I have done much looking ,digging,and contemplation of the minutia of both head stamps 308/7.62 NATO ,and have concluded this . They are of identical external denintions,execeptions for tooling and actual shoulder radia. The NATO cases are thicker brass as are several Match years from LC. NATO chambers are loose to feed everthing made everywhere from America to Zimbobwia(sic),clean,dirty,rusted,corroded,dinged, buldged,steel, brass,copper at -60 to 140*, see the fluted HK(?)chamber for reference. Also there are 3 gauges in GI service ,GO NO/GO and field. The field gauge is longer than the NO/GO and allows an absolute maximum dimention for the last ditch,cut supply line,it still goes bang but it ain't right rifle.

The above is my belief based on the research of the NATOs ,5.56,7.62 and 9mm,and results from combined reading from the www and hard copy as well as the hands on measurement of cartridges from 50 plus commercial sporting and GI arms both current issue and free market and new surplus ammo from Europe,Asia and So.America.

I've had an issue with NATO brass and LC match in a Savage 308 that was cured with a neck ream and trim.

All good information gentelmen.

[nicholst55]

TECHNICAL MANUAL 43-0001-27
US ARMY AMMUNITION DATA
JUNE 1981

I have no idea if this information is out of date or not. Every cartridge type listed for the caliber shows a chamber pressure of 50,000 PSI.
http://fgsp.files.wordpress.com/2011/04/photos6-e1302803693328.jpg

The chamber pressure posted in that TM is merely the nominal figure - the 'perfect world' scenario. Actual chamber pressures, bullet weights, powder types, and powder charges will vary during production runs. My advice is to use the data listed there as a guide only.

[Larry Gibson]

That is a CUP "psi" measurement.

TM 9-1305-200 states; "Pressure Test. This test is conducted in a pressure barrel. The barrel chamber is drilled with a small hole into which is inserted a metal piston. On firing the cartridge, the pressure of the gases force the piston against a copper cylinder and compresses it. The amount of compression of the cylinder is an indes of the pressure developed."

That is a C.U.P. pressure measurement. The same TM also state the psi for the M58 7.62 NATO cartridge is "50,000 psi".

Old psi measurements made with CUP pressure barrels are different from the peizo measurements made today. That is most where the confusion comes with comparison of .308W with CUP, old psi measurements and new psi measurements etc.

Larry Gibson

[spqrzilla]

For those who do not understand what Larry and I are saying, go look at the online data on the Hodgdon website for .308 Winchester. You'll see different load data for the cartridge expressed in CUP and PSI that you can contrast. You'll see that actual psi pressure measurements are higher than pressure expressed in CUP. The tech specs that Jim copied say "psi" but really are CUP and that's why they appear to show the military ammo as being spec'd a lower pressure than SAAMI .308 Win.

But as Larry and I have argued here, that's caused by confusion of what the specs are expressed in.

[badbob454]

i shoot both in both rifles ... the big deal is the 7.62 has more brass in the case = higher pressure, all things being the same "same primer , powder , and bullet " so back off a little in surp 7.62 cases ,,when reloading ... no arguments here

[sqlbullet]

sqlbullet

My apologies ...

I appreciate the concern about safety. If one is not familiar about loading for 7.62 gas guns then one best stick with milsurp cases. However, with regular dies and regular FL sizing incipieant case head seperation will still occur after several firings. Is it any "safer" if case head seperation occurs on the first load or the 4th or 6th? Best of avaiod case head seperation all together, eh?

Larry Gibson

No apology needed from you Larry! You contribute way to much!

And, definitely on the same page about safety. If you don't know your gun, regardless of cartridge, you will be in for some nasty surprises at some point when reloading.

[Multigunner]

Chamber pressure of U S M80 Ball is 48,000 CUP or 50,000 PSI Epvat The NATO standard pressure test method).
M118 pressure is listed only in Copper Units of Pressure at 52,000 CUP.
Those are average working pressures. Sample cartridges from a production lot of M118 can generate up to 57,000 CUP and the lot still be accepted, so long as the average pressure of test samples remains at or below 52,000 CUP.


Theres no direct correlation between CUP and PSI Epvat pressures from cartridge type to similar cartridge type or the same cartridge type with different bullet weight and performance.
The supposed 10,000 PSI difference as a rule of thumb just doesn't work.

As commercial Long Range Target ammunition has begun to push the limits for the .308 Winchester many older rifles proofed for the NATO Standard Ball, which is supposed to be within the 48,000 CUP limitation of M80 Ball, will have to be re-proofed if they are to be used on UK NRA ranges and using the long range match ammo supplied by the NRA.

The 2A rifles and converted No.4 and 93/95 Mauser rifles, if in good condition, should handle NATO Ball and commercial sporting cartridges loaded with 150 gr bullets and at standard velocities without problems. Some Commercial .308 and M118 Special Ball may be unsuitable for the older rifles and would at the least cause excessive wear and stress on the action.
.308 Win cartridges loaded with bullets heavier than 150 grains may be okay so long as the pressure level is in the 48,000 CUP range.

Problems with Winchester commercial ammo in autoloaders is often due to high gas port pressure causing the action to begin to unlock to early while chamber pressure is still high.

[Larry Gibson]

Multigunner

Not sure where you got that info but MIL-C-46931F (AR) dated 31 March 1989 states the chamber pressure of M80 ball at 70 degrees by copper-crush cylinder test method the average chamber pressure shall not exceed 50,000 psi. The average pressure plus 3 standard deviations shall not exceed 55, 000 pso. The chamber pressure of an individual sample cartridge shall not exceed 55,000 psi.

Chamber pressure by EPVAT test method The average chamber pressure of the sample cartridges at 70 degrees shall not exceed 52,940 psi. The average chamber pressure plus three standard deviations of the chamber pressure shall not exceed 58,016 psi. The chamber pressure of an individual sample cartridge shall not exceed 58,016 psi.

M118 and M118 SB is also held to 50,000 average psi (CUP) with 3 standard deviations not exceed 55,000 psi (CUP).

EVPAT (Electronic Pressure, Velocity and Action Time) testing is currently controlled by SCATP-7.62 which states; “Chamber pressure. The average chamber pressure of the sample cartridges conditioned at 70 degrees +/- 2 degrees shall not exceed 65,000 psi.” (this certainly is right up there with the current SAAMI PMAP of 62,000 psi for the .308W)

Are we confused yet? As I've stated earlier; I've been pressure testing quite a few different lots of 7.62 NATO ammuntion. I can say that with US made M80 and M118 WB, M118SB and M118LR that the pressures have remained fairly consistent throught their production. This is particularly the case with M80 as I've tested lots from as far back as WRA69 up through LC 2002. All have been within NATO spec and there is no evident trend toward higher psi. The same holds for M852, M118SB and M118LR. Of the lots I've tested I find no trend toward higher psi's. The current psi's remain consistent with M118 WB dating from LC65.

Perhaps in the UK things are different but from the 2 lots of Radway Green (SP?) 7.62 I've tested they seem consistent with other nations 7.62 for FN-FAL specific weapons.

Larry Gibson

[Multigunner]

Multigunner

Not sure where you got that info but MIL-C-46931F (AR) dated 31 March 1989 states the chamber pressure of M80 ball at 70 degrees by copper-crush cylinder test method the average chamber pressure shall not exceed 50,000 psi. The average pressure plus 3 standard deviations shall not exceed 55, 000 pso. The chamber pressure of an individual sample cartridge shall not exceed 55,000 psi.

Chamber pressure by EPVAT test method The average chamber pressure of the sample cartridges at 70 degrees shall not exceed 52,940 psi. The average chamber pressure plus three standard deviations of the chamber pressure shall not exceed 58,016 psi. The chamber pressure of an individual sample cartridge shall not exceed 58,016 psi.

M118 and M118 SB is also held to 50,000 average psi (CUP) with 3 standard deviations not exceed 55,000 psi (CUP).

EVPAT (Electronic Pressure, Velocity and Action Time) testing is currently controlled by SCATP-7.62 which states; “Chamber pressure. The average chamber pressure of the sample cartridges conditioned at 70 degrees +/- 2 degrees shall not exceed 65,000 psi.” (this certainly is right up there with the current SAAMI PMAP of 62,000 psi for the .308W)

Are we confused yet? As I've stated earlier; I've been pressure testing quite a few different lots of 7.62 NATO ammuntion. I can say that with US made M80 and M118 WB, M118SB and M118LR that the pressures have remained fairly consistent throught their production. This is particularly the case with M80 as I've tested lots from as far back as WRA69 up through LC 2002. All have been within NATO spec and there is no evident trend toward higher psi. The same holds for M852, M118SB and M118LR. Of the lots I've tested I find no trend toward higher psi's. The current psi's remain consistent with M118 WB dating from LC65.

Perhaps in the UK things are different but from the 2 lots of Radway Green (SP?) 7.62 I've tested they seem consistent with other nations 7.62 for FN-FAL specific weapons.

Larry Gibson

I got the chamber pressure figures from a much more recent document, on standards for propellents and such in procuring ammunition.
A had a crash recently that erased all my files, had to do a destructive reinstallation of the OS in order to get this PC up and running again. I've been trying to find that document again at Every Spec, but its not easy to search that site if you don't have the title of the document handy.

I've posted a link to that document several times, and probably on this board somewhere. I'll take another look for it at Every spec and post a link when I find it.

The NATO Standard Ball manufactured by Radway Green was a 144 gr bullet and in the 48,000 CUP range just as all NATO Standard ball should be wherever manufactured, but theres some variation.
The British also use a 155 grain bullet load, its not the NATO Standard which was set for interchangeability.
The NRA UK matchgrade ammunition that caused the reproofing controversy is not manufactured by Radway Green, its manufactured for the NRA under contract outside the UK.

Australia used only single base powder for its 7.62 ammo intended for the FN FAL, some cartridges loaded with double base powders deliver too high a gas port pressure and the action tries to open while chamber pressure is still high enough that the case grips the chamber wall.
I've seen this happen with Winchester Match grade cartridges, with regulator turned down as far as it would go and still function. The rims were badly distorted and almost torn off.
The M14 shouldn't have that problem, it was designed around double base ball powders, and its gas system makes allowances for variations in port pressure.

M118 and Long Range Special Ball are presently loaded to chamber pressures somewhat higher than M80 Ball. The only pressure figures listed in the document I refer to for the M118 and Long Range as the document said would be the new designation were expressed in Copper Units of Pressure.
The Chamber pressures for M80 Ball were expressed in both CUP and in PSI EPVAT.

So long as performance figures are met a significantly lower pressure in testing is allowable, but gas port pressures must also be kept within certain limits to insure proper function of gas operated weapons.

Heres the document from 1998
http://www.everyspec.com/MIL-SPECS/MIL+SPECS+(MIL-P)/download.php?spec=MIL-P-3984J(AMENDMENT3).008538.PDF
MIL-P-3984J
AMENDMENT 3
12 June 2000
SUPERSEDING
AMENDMENT 2
30 July 1998
MILITARY SPECIFICATION
PROPELLANTS FOR SMALL ARMS AMMUNITION
This Amendment forms a part of MIL-P-3984J dated 25 May 1992, and is approved for use by
all Departments and Agencies of the Department of Defense.

(For 7.62MM, change “Special Ball M118” to “Long Range M118”, and change “Match
/16 M852” to “Match M852”)


The propellents in use in recent years for M118 Long Range may generate higher pressures than those formerly used for M118 Special Ball.
IIRC M118 LR uses RL-15 powder only.

PS
I just reread the specs
M80 Ball average working pressure is listed as 48,000 CUP/51,000 PSI EPVAT, maximum std deviation is 53,000 CUP/56,000 PSI EPVAT.
M118 Long Range average working pressure is 52,000 CUP (no EPVAT equivalent) , maximum std deviation is 57,200 CUP.

[Larry Gibson]

Multigunner

I imagine the figures are going to be somewhat different because the US and NATO are now using piezoelectric transducers at the case mouth for production testing as the standard piezoeletric transducer located on the case body requires drilled cartridge cases which is somewhat cumbersome. Thus there are two seperate psi's, one for each test method and both are correct. That just reinforces the contention that it is all dependent on whose figures you read and how those figures were obtained. The difference has lead to the confusion. Additionall those figures are generally MPSMs (Mean Probable Sample Mean) or MPLMs (Maximum Probable Lot Means) not what the actual MAP (Maximum Average Pressure) of the production ammunition may, in fact, be.

My point is that I've been measuring pressures, yes actually measuring them....not just taking "report figures" as fact. The actual measurement of pressures of most NATO spec (there is a lot of milsurp stuff that is not NATO spec BTW) M80, M118SB and M118LR do not show a trend toward higher psis. That is from actual measurement of said ammunition in the same test rifle using the same test means. One can argue psi's all one wants citing any multiple of reports or documents that only give acceptence standards for ammunition in MAP, MPLM or MPSMs. Most of those acceptence stands are maximum allowable, not what the actual production ammuntion really does psi wise. Actual measurements of psi of production NATO spec ammuntion show that the MAP psi's obtained are usually below those reported as the maximum acceptable in all the documents cited.

This is the same situation with the .308W. All the "documentation" most everyone cites quotes SAAMI PMAPs at 60 or 62,000 psi. Many then assume every factory cartridge of .308W is loaded to that psi. Such is not the case just as 7.62 NATO spec ammuntion is not generally loaded to the MPLM as listed in the reports/documents cited as NATO Specs. Some lots of both .308W and 7.62 NATO spec ammuntion is loaded pretty close but I've not found any that exceeded specification either SAAMI or NATO. However, I've found most of both types isn't loaded to the MAP or the MPLM. As I stated earlier in another post, the psi's of 7.62 NATO spec ammuntion over lap that of the .308W factory ammuntion. One can not say for any certainty that one is of higher pressure than the other. One can not say with any certainty that shooting either one is "safer" than the other. This is from actual measurment of psi taken with various 7.62 NATP spec ammunition and several different .308W factory ammunitions. It is not from assumptions made reading confusing PMAPs from various documents taken from different test methods.

BTW: NATO specs for M80 has a criteria for bullet weight and velocityalso. Pushing a 140 -155 gr bullet to 2750 +/- 20 fps (at 78 ft from muzzle) does not require the psi of any of the listed MPLM/MAPs listed given an appropriate powder that meets the gas port pressure requirement. I've found numerous lots of .308W that also do not exceed the NATO MPLM/MAPs even when pushing a 150 gr bullet at 2850 fps. M118SP and M11LR most often have PMAPs that are equivelent of top end .308W ammuntion but do not exceed published MPLM/MAPs. Again, all from the same test rifle with the same test method (M43 Oehler).

Larry Gibson

[Char-Gar]

I am a practical/hands on sort of fellow, so I went to my bench and dropped a couple of LC68 7.62 Nato rounds in a Wilson .308 Winchester gage. The rounds showed perfect headspace on the Wilson gage.

All of the pressure talk not withstanding, that tells me the difference is in the military vs. commercial chambers and not the ammo.

That settled it...for me anyhow.

[NHlever]

Be aware that some manufacturers use the NATO chamber, or did at one point. Ruger is one example that I know about. The barrels are stamped .308 Win. but the chambers are the nato dimensions.. I think that is one reason that some .308's that I have had just wouldn't display that "inherent" accuracy that the .308 is supposed to be famous for. Bottom line as far as that goes seems to me to be cartridges that fit the chambers, and barrel diimensions that are as they should be for the full length of the barrel.

[pilot]

Has anyone here personally blown up a rifle using the "wrong" ammo yet?