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7.62 NATO and .308 Winchester

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Alan de Enfield View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alan de Enfield Quote  Post ReplyReply Direct Link To This Post Posted: November 04 2009 at 12:54am
Whilst 308 and 7.62 may look the same, in fact (as has already been said) the NATO cases are thicker brass and hence have less space inside, a similar amount of powder in a 7.62 will have less space than in a 308 and hence the pressures will be considerably different, add to this the fact that NATO 7.62 chambers are a different size to commercial 308 and all sorts of problems can occur.
 
Put a 308 cartridge into a 7.62 chamber and you've immediately increased your headspace by 0.013" (13 thou)
 
If it says 7.62 on the rifle use 7.62, if it says 308 use 308.
 
"Use what it says on the tin"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldbikewrench Quote  Post ReplyReply Direct Link To This Post Posted: November 04 2009 at 11:49am
I am not a ballistician so I can't get all technical, but I bought a CETME a little while back and was told that yes it would shoot off the shelf .308 Winchester ammo. Well it did indeed fire one round and that case was perfectly fire formed. And for those that don't know, the CETME has a fluted chamber. That case was really stuck in there. Had a heck of a time getting it out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Unauthorized Quote  Post ReplyReply Direct Link To This Post Posted: November 04 2009 at 12:00pm
The Brits sanction the use of #4s with only one 7.62 load the 144 grn Nato version.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: November 04 2009 at 10:30pm
While agreeing with the point raised on brass thickness having the side effect of reducing internal volume this can simply be compensated for by using an appropriate powder charge for that volume.
This is a basic re loading technique with any brass, or caliber.
 
When all the measurements are taken & compared & all the thoeries are expounded on there is still one question that no-one who is a suppoerter of the "It's different" train of thought have been able to answer for me personally, so I'll ask it again.
 
IF there is a real, functional difference between MilSurp 7.62mm NATO, & .308 Winchester commercial ammunition why is it that I've been able to fire both factory-issued ammunition & my own reloads in both commercial .308 Winchester & 7.62mm NATO chambers with complete interchangability for the last 15 years without incident, regardless of the combination used?
 
This would seem to indicate that real problems regarding complete functional interchangability do not exist.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Unauthorized Quote  Post ReplyReply Direct Link To This Post Posted: November 24 2009 at 12:37am
Were any of your rounds actually fired in a converted #4 Lee Enfield?

Rifles designed for either round would probably be ok.
The #4s are approved by the Bits only of the 144 grn 7.62 Nato load. They were not designed for either round.
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Alan de Enfield View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alan de Enfield Quote  Post ReplyReply Direct Link To This Post Posted: November 24 2009 at 1:09am
Originally posted by Unauthorized Unauthorized wrote:

Were any of your rounds actually fired in a converted #4 Lee Enfield?

Rifles designed for either round would probably be ok.
The #4s are approved by the Bits only of the 144 grn 7.62 Nato load. They were not designed for either round.
 
The UK NRA did indeed issue a warning regarding the use of heavier than 144 gr 7.62 bullets in converted NO4 actions - stating that there was risk of catastrophic failures.
Here is a 'cut and paste' of the warning.
 
NRA Safety Warning
Enfield Rifle Actions Converted to 7.62 Calibre from .303 or made as 7.62 mm. Enfield actions of the No 4 and No 5 type were originally designed to fire the British .303 service cartridges of the day.
Many of these actions have been subsequently converted from .303 to 7.62 mm. Whilst a few selected actions may be stronger than others, most are not suitable for use in this calibre other than under certain conditions.
The 7.62 mm Cartridge that they were intended to use was the 144-grain NATO cartridge with a bullet diameter of .3075".

It is unsafe to fire these rifles with the 155 grain Radway Green cartridge or any other commercial cartridges using the 155 grain or heavier bullet which has a diameter of .3083" or larger.

 Firing these latter cartridges can ultimately lead to catastrophic failure of the bolt lugs and bolt body that could lead to serious injury. This risk is considerably increased if the chamber or cartridge gets wet or is oiled prior to firing.

The NRA will not accept responsibility for any accident or injury to persons or property caused by anyone using any 7.62 / .308 Win ammunition supplied by them in these converted actions.

The actions/rifles involved the following descriptions,but ther may also be other names or descriptions,SMLE Conversion,Enfield Conversion,No4 Conversion, No 5 Conversion,Parker Hale T4,Whitaker Special, Enfield Envoy and Enfield Enforcer

 
I have heard (no confirmation) that under the threat of legal action the NRA has been forced to withdraw that statement as they can offer no evidence of any kind to support their claim. (The notice has certainly been removed from Bisley)
 
Again - speculation, but it is thought that an NRA 'official' read something on the internet and took it as 'gospel'.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LE Owner Quote  Post ReplyReply Direct Link To This Post Posted: December 04 2009 at 7:45am
Perhaps this will shed light on the warning which seems to be directed at those rifles fitted with barrels tighter than the more common .308 dia.
 
 
The early manufacture FN FAL barrels in British service also had exceptionally tight bores, the reason given was to greatly increase bore life.
Those barrels are said to have been about one thousandth smaller (perhaps less) in land to land and groove to groove measurements. Apparently the British manufacture 144 gr ball used a bullet suited for the tighter bore, later 7.62 ammo types appear to be less suited to the tight bores and can result in significant increase in pressures when fired in a tight bore. 
 
The difference between 7.62 NATO ball and the hottest .308 loads is much like the difference between the .38 ACP and the .38 Super Auto, or the 9mm Glisenti vs the 9mm Parabellum. Dimensionally they are twins, but not all guns manufactured for the earlier cartridge can handle the pressure of the later cartridges.
 
The No.4 Enfield was not manufactured in 7.62 NATO caliber, it was converted to that chambering to use the NATO standard ball, which generates 48,000 CUP or 50,000 PSI Epvat.
The Indian 2A rifle was manufactured in 7.62 NATO, the Indian 7.62 Ball (India is not a NATO member) also generates the same pressures, circa 48,000 CUP or 50,000 PSI.
So long as your rifle is in good order and you chose your ammunition wisely there should be no problems, there are many .308 loads which are at or below 48,000 CUP or 50,000 PSI, but there are also loads which exceed this pressure range by 10% or more.
 
When bullets heavier than 150 gr are used with either 7.62 or .308 the maximum standard deviation in pressures can skyrocket. A 175 grain Special ball cartridge rated at 52,000 CUP has a Max Std Dev of 57,000 CUP 18% higher pressure than the operating pressure of Nato ball.
 
 
PS
Other similar cartridge and rifle combinations would be
The 1895 Winchester in .30/06 caliber, safe enough when cartridges generating pressures no higher than the original 150 gr bullet WW1 era load is used, but long noted for developing excessive headspace when the later 172 gr and WW2 era Ball ammunition and commercial sporting rounds of similar pressure levels were used.
 
The Gew 1888 in "8mm Mauser" chambering, safe enough when pre WW1 8mm ( J bore .318 bullet , .321 bore) cartridges loaded with bullets of .318 to .321 are used, and considered reasonably safe for use with the medium pressure Remington 8mm Mauser sporting ammo (loaded with the .321 bullet developed for the .32-49 and .32 Winchester special) is used, but not so safe when 7.92 S bullet (.323) cartrdges loaded to WW1 and later pressure ranges, and a disaster in waiting should a WW2 era 7.92 Heavy Ball MG or LMG cartridge be used.
Some of these rifles were modified with .323 bores, but even then the metalurgy is suspect and the rifle is not considered suitable for the later Mauser cartridges.
Chambers are the same and cases are pretty much indistinguishable.
 
 
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Alan de Enfield View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alan de Enfield Quote  Post ReplyReply Direct Link To This Post Posted: December 04 2009 at 4:03pm

 
I have no knowledge on this subject so could not comment - however I do not see the relevance of this statement on a thread about 7.62 Vs 308.
 
Any personal 'attacks' should be removed by the moderators before the battles commence.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LE Owner Quote  Post ReplyReply Direct Link To This Post Posted: December 04 2009 at 4:52pm
While Norton's portrayal of David Banner in the most recent big screen version of the Hulk was uninspired and left much to be desired I would not go quite that far.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Quote  Post ReplyReply Direct Link To This Post Posted: December 04 2009 at 5:55pm
I suggest you delete your comment charly45 or I'll do it for you!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SW28fan Quote  Post ReplyReply Direct Link To This Post Posted: December 05 2009 at 3:58am
We really don't need personally attacks hear.  I would be happy to see this thread vanish but the Issue of CUP vs PSI has come up.  I once asked a co-worker who is both a shooting enthusiast and  a PhD in metallurgy what is the difference between them and is there a conversion.  The short answer is  they are different animals and not parallel running scales. The conversion is somewhat complicated.  Since simple Triginometry is the absolute zenith of my mathamatical ability I did not press further. The point is that a difference of 2000 in CUP can mean a great deal of pressure.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LE Owner Quote  Post ReplyReply Direct Link To This Post Posted: December 05 2009 at 6:18am
If what I've read on the subject is correct, and I didn't misread it which is a possibility, the US method of measuring chamber pressure by CUP may have been developed by the French in the late 19th century.
The British base thrust method is aimed at determining the actual back thrust to the breech face of cartridges in the dry condition and when cases are lubricated, The British method in use while the Enfield was still a battle rifle does not read actual chamber pressures but rather back thrust in long tons.
The French and US Ordnance methods read Chamber pressures at a chosen spot on the cartridge case or by direct gas inpingement by means of gas bled off at the case mouth to drive the piston. The ammunition being first heated for a period of time to mimic cartridges left in a chamber already warmed by having fired a number of rounds.
The best figures I've found for the British MkVII cartridge as measured in CUP by the US Ordnance method is 45,400 CUP at 60 degrees, I found this information in an article on the P-14 rifle in the Journal of the Franklin Institute, quoted from a book written by a US Ordnance Officer.
In general CUP figures found in manuals are rounded to the nearest 1000, thus the commonly published figure of 45,000 CUP.
 
The more modern EVPAT test figures used for NATO spec ammunition are taken using a piezo electric crystal and expessed as PSI.
Ammunition types not commonly interchangable may not be measured by the EVPAT method, so we have Long range Special Ball measured by the older Copper Units of Pressure.
Standardized 7.62 NATO Ball in US inventory is measured by both the EVPAT and CUP methods, both figures are given in some government publications. Unfortunately some less informative manuals don't make the distinction and this can lead to confusion.
 
The 7.62X51/.308 cartridges have features which can make chamber pressures a bit more critical where heavier bullet long range Match or Sniper ammunition is concerned.
The limitations on OAL of the cartridge, its short OAL being a major design feature, result in longer heavier bullets taking up space in the powder space, effectively reducing available case capacity and resulting in higher pressures to achieve the same performance as a similar load in a cartridge with greater OAL.
When first adopted the intention was to benefit from advances in propellant technology to allow the shorter cartridge to equal the performance of the earlier loadings of the .30/06 without any noticable increase in pressures. This they managed to achieve but only in loads that used bullets of 144-150 grains or less. When heavier bullets are used pressures begin to climb compared to the .30/06 or the .303 for that matter.
When case capacity is restricted by the protrusion of the base of the bullet into the case the normal situation of deviations in maximum pressures are agravated.
 
Add to the above the simple facts that ammunition is declared surplus for the following reasons, over production, obsolesnce, failure to pass the now standard five year inspection of NATO ammunition stocks.
The 7.62 may be less commonly used by infantry rifles than before, but it is far from being obsolete and millions of rounds are being eaten up by GPMGs the world over. Over Production is not an issue since every available round that can pass inspection is needed either for combat or as reserve stock or given to allies. That leaves failure to pass inspection.
So when you seen 7.62X51 ammo sold as surplus these days it almost certainly came from a lot which failed its five year inspection process, and may well have failed that inspection decades earlier and suffered even more degradation from poor storage since then.
Rather than the ammo having one or two cartridges per thousand that develop the maximum deviation of 57,000 CUP a degraded lot might far exceed that figure at every shot from a twenty round box.
In worst case scenario all those variables might combine and a rifle could be subjected to excessive pressures at every shot through hundreds of rounds in a short time.
 
When looking up info on the Enforcer Police sharpshooter rifles I found that the British MOD had at one time released a number of L42 Sniper rifles for police use. These rifles were inspected by the police and found to be dangerously degraded and judged unsafe to fire. The L42 should have been the one converted No.4 action rifle least likely to have suffered such degradation in service. sniper rifles seldom fire as many shots in anger during their entire service life than an infantry rifle might fire in one week of a WW2 campaign.
The L42 should have also been fed only the best available of the approved ammunition type, the 144 gr ball.
Asking a recognized authority on these rifles about the ammunition approved for use with the L42 resulted in no useful information at all. A simple question, one that should have taken only a few words to answer, appeared to generate hostility out of proportion to the subject. In the end no answer other than a vague prohibition against use of non military ammo was given.
 
If ammunition other than the 144 gr ball was used with the L42 towards the end of its service life this might explain those abused rifles the British police depts turned down.
 
I also ran across a discussion on a British military 7.62 ammunition type which has the designation L42 , but which was not in fact meant for use by the L42 rifles. Perhaps a mix up had resulted in an unsuitable ammunition being issued with those rifles, and damage to the actions was the result.
 
 
PS
The major stumbling block to finding out anything useful about the converted No.4 rifles seems to be the emotional attachment some owners and former servicemen have towards the Enfields.
As far as I'm concerned emotional attachments are best reserved for living things.
 
When emotions and personality conflicts intrude any chance of calm discussion and judgements based on fact go out the window.
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Quote  Post ReplyReply Direct Link To This Post Posted: December 05 2009 at 6:22am
I have deleted the personal comment made on here! I suggest every member plays nicely or I WILL lock this forum again once and for all.
         Tony.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: December 05 2009 at 7:07am
Let me try to clarify things a bit here.
There are basically 2 seperate issues being mixed together, & this is adding fuel to a burned out fire.
 
1. There is zero practical difference between correctly loaded 7.62mm NATO and .308 Winchester commercial ammunition in rifles built for either "caliber". (quotes intentionally used.)
 
2. It is possible to intentionally create a bad to dangerous load in either caliber, but why would you other than to prove a point erroniously by damaging a perfectly good firearm & possibly injuring a fellow shoter, just to make an essentially pointless point.
 
OK, having gotten that out of the way.
 
Some rifles are not designed for some loads, even in the (nominally) correct caliber. As an example I offer the Garand (a perfectly good rifle) being loaded with heavy bullets & slow burning powders. Yes you could mess up a Garand, but why would you, just to proove a point? The Garand was designed for a particular function, & it does that well. Can It be messed up? Heck yes, so can you think of a reason why you'd actually do this? I thought not.
 
There is a very good discussion on the .308/ 7.62mm non-issue right here on this forum, I respectfully suggest you actually read that thread first before bringuing this unicorn jousting non-issue up here as a seperate item.
After all there is no suggestion that the Garand is incapable of digesting 30-06 ammunitioin, because bad 30-06 loads can be developed, so whyn is there this silly discussion on the 7.62mm Enfield conversions being incapable of digesting suitable ammunition as well?
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: December 05 2009 at 7:13am
"If it says 7.62 on the rifle use 7.62, if it says 308 use 308."
That would make perfect sense, except that one part of my rifle says 7.62mm & the other says 3.08 winchester!
Using the logic you suggest should I use both interchangably, or neither?Geek
Even worse!!
I reload:
Shouild I use .308 Winchester dies, or 7.62mm NATO diesStar
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Smokey Quote  Post ReplyReply Direct Link To This Post Posted: December 05 2009 at 8:56am
In all honesty, I would get a bunch of once-fired 7.62mm Military brass, and reload it  using either .308 Winchester or 7.62mm dies. I would NOT try to duplicate the ballistics of either load though. LOL
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