Gun Proof in India - An Historical Account

With all of the recent attention being paid on these forums to the Lee Enfield and proof pressures, I thought the following extract would be of value to some of you - I certainly don't want it to start another ruckus :thdown:

I have an awful lot of reference material and while reading today I came across a paper titled "Gun Proof in India - An Historical Account." It was written by Mr. A. G. Harrison the former Proof Master at the Rifle Factory Proof House, Ishapore, India and was published in "The Gun Digest, 33rd Edition, 1979."

I'll get it scanned later but for now I've extracted the part that interested me:

From 1908 to 1950 all military bolt action rifles made at Ishapore were proof tested with a dry proof round followed by an oiled proof round. The proof cartridge was loaded to 24 tons (2240lbs = 1 ton) psi breech presure, or 25% higher than the service pressure.

In 1950 the material for rifle bodies (they made No.1 Mark 3* rifles; my addition) was altered from an EN steel to SWES 48 steel (not heat treated) except for the recoil shoulder and cam recess in the receiver. With this change the rifle receivers distorted when oiled proof cartridges were fired. This was discovered when hard and sometimes impossible bolt retraction was experienced. Large quantities of rifles were rejected. To avoid rejections the authorities ordered discontinuance of the oiled proof. Therefore from 1950 to the end of SMLE rifle production (June 1965) rifles made at Ishapore were proof tested with one dry proof only, although the specification called for both dry and oiled proof.

A bolt action rifle similar to the SMLE Mk. III*, modified to fire the 7.62 NATO cartridge was produced at Ishapore, first in February 1965. Their receivers were made of SWES 48 steel, un-heat-treated, and with the NATO proof cartridge receivers were found to distort with the oiled or the dry proof round! The material was changed to an EN steel so now the rifles stand up better to dry and oiled proof.

There's a lot you can read into what the author has said but I am not going to make any assumptions.

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Originally Posted by Amatikulu

There's a lot you can read into what the author has said

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I'll drink to that, for sure. :beerchug:

That's intersting Amat. Like I said, we tested the rifle body steel from Indian 7.62 AND .303" SMLE's and contrary to popular belief, they were all the same...., within the realities/peramaters of steel mixing of course.

Me .... I think I´ll keep my 7.62 chamber (very) dry in future. When I recently got the rifle, rounds would not fall into the chamber of their own weight and were sticky extracting. Sent the action to Germany´s leading gunsmith (head of the German guild of gunsmiths and maker of gunsmith tools, mainly reamers). He inspected the chamber and tested head space. Told me that headspace was not up to German commercial standards, but well within limits.The chamber was re-reamed in the shoulder area and is now spot on and I now only have to neck size. I didn´t like the alternative advice given by my re-loading expert who advised the use of a special (smaller) die, made for full auto and machine guns. So, is there a difference in size between 7.62 full auto cases and commercial?

Peter, the way I read what Mr. Harrison published, the Mark 3* up to 1950 and the 2A/2A1 rifles from 1965(apart from inital 1965 production) were made with EN grade steels - confirming exactly what you found in practice.

There was once a theory circulating that the 2A/2A1 rifles were made from a different steel to allow the use of 7.62 NATO ammunition. It would seem that was not the case. The explanation is that from 1950 to 1965, Ishapore made receivers for the Mark 3* in a different steel grade. Due to the dropping of the oil proof during this period, it is obvious that it was not as strong as the EN grade of steel. SWES 48 was only just strong enough to allow dry 303 proof and was not at all suitale for 7.62 NATO proof (dry or oiled).

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Originally Posted by villiers

Me .... I think I´ll keep my 7.62 chamber (very) dry in future. When I recently got the rifle, rounds would not fall into the chamber of their own weight and were sticky extracting. Sent the action to Germany´s leading gunsmith (head of the German guild of gunsmiths and maker of gunsmith tools, mainly reamers). He inspected the chamber and tested head space. Told me that headspace was not up to German commercial standards, but well within limits.The chamber was re-reamed in the shoulder area and is now spot on and I now only have to neck size. I didn´t like the alternative advice given by my re-loading expert who advised the use of a special (smaller) die, made for full auto and machine guns. So, is there a difference in size between 7.62 full auto cases and commercial?

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Villiers
Here in central Pennsylvania the Remington 760 pump action is very popular for hunting in the woods where fast follow up shots are needed at running deer. Several people I hunted with were given the same advice as you were and they used small base reloading dies and all of them suffered the same problem, premature case head separations from over sizing the cases. If anything the 760 has a larger diameter chamber and longer headspace, I always used a full length die set to only partial resize my cases and never had any case head separations.
The bottom line was I never owned a rifle that needed small base dies, American made cases are on the small side on base diameter anyway.

RCBS Reloading die FAQ

Q. I see a Small Base Die Set listed for my caliber. Do I need these or should I buy a Full Length Die Set or Neck Die Set? How does each set differ?

A. The Small Base Die set is intended for use for ammunition to be used in auto, semi-auto, and lever action rifles so that the loaded round chambers and extracts easily. The Small Base Sizer Die sizes the case from the shoulder to the head of the case a couple of thousandths smaller than a Full Length Sizer Die. In certain calibers it also sets the shoulder of the case back a thousandth or two more than the Full Length Sizer Die. The Full Length Die Set or Neck Die Set is not normally recommended for ammo to be used in auto, semi-auto, or lever action rifles. The Full Length Die set is recommended for ammunition used in bolt action rifles, particularly for ammunition to be used for hunting. The Neck Die Set can also be used to produce ammunition for use in bolt action rifles. The Neck Sizer Die sizes only the neck of the case so it will hold the bullet firmly. It does not size the body of the case nor does it set the shoulder back. Neck sized cases will usually chamber for three or more firings, depending on the powder charge and chamber dimensions. However, over a period of time, a slight drag will be noticed when the bolt is locked. At this point, cases will need to be full length sized and the shoulder set back so they will chamber and extract easily.

In my 760 pump I could neck size the cases twice and the cases would eject correctly BUT on the third firing I would have to wait for the case to cool for 5-10 seconds before they would eject. For hunting all cases were full length resized and for range practice headspace control shims or washers were used under the die lock ring to partially resize the case.

Ed, I use a f/l RCBS die for my 7600 in .308 and only partly resize the cases. I run them into the die a little more than 2/3 of the length of the neck. At least in my rifle this works great. Chambering and extraction is always reliable and easy.

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Originally Posted by Peter Laidler

That's intersting Amat. Like I said, we tested the rifle body steel from Indian 7.62 AND .303" SMLE's and contrary to popular belief, they were all the same...., within the realities/peramaters of steel mixing of course.

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Is the EN steel a Chrome Nickel Steel?
Skennerton's book , if that where the scanned page I saw earlier came from, stated that the Lithgow rifles that failed the tests when converted to 7.62 were (near as I remember) "degraded by use of Carbon Steel rather than Chrome-Nickel Steel".
Australia has large deposits of Nickel, so a Nickel Steel alloy would be logical for the Lithgow receivers. Nickel Steels are more elastic, and these alloys were invented by an Englishman.

If you have the specs for this alloy it would be useful.

I've found the specs for the US M1917 rifles, which I figured were the same as that used for the P-17. Its a high nickel content steel.

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1917 Enfield Rifles

Receiver and Bolt:
Made of nickel steel specificed in US Army Pamphlet no. 3098.
This steel could be made by the acid process, or the basic process, both were accepted.

Acid Process:
Carbon .30% to .40%
Manganese .50% to .70%
Nickel 3.00% to 3.75%
Phosphorus under .05%
Sulphur under .035%

Basic Process:
Carbon .35% to .45%
Manganese .50% to .70%
Nickel 3.25% to 3.75%
Silicon .10% to .20%
Phoshorus under .05%

Barrel Steel specified in US Army Pamphlet no.3098:
Carbon .45% to .55%
Manganese 1.10% to 1.35%
Silicon .20% to .30%
Phosphorus under .06%
Sulphur under .06%

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Quote:

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Originally Posted by villiers

Me .... I think I´ll keep my 7.62 chamber (very) dry in future. When I recently got the rifle, rounds would not fall into the chamber of their own weight and were sticky extracting. Sent the action to Germany´s leading gunsmith (head of the German guild of gunsmiths and maker of gunsmith tools, mainly reamers). He inspected the chamber and tested head space. Told me that headspace was not up to German commercial standards, but well within limits.The chamber was re-reamed in the shoulder area and is now spot on and I now only have to neck size. I didn´t like the alternative advice given by my re-loading expert who advised the use of a special (smaller) die, made for full auto and machine guns. So, is there a difference in size between 7.62 full auto cases and commercial?

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I ran down the personal account of the Sniper whose L42 jammed so badly in combat in the Falklands campaign that he discarded it and used a captured Argentine FAL in its place.
He said that the weather was very wet and the bolt became so still he could barely operate it. He blamed the problem on not having had any oil to put on it, but I've never seen an Enfield that wouldn't cycle without lubrication.

Its likely German standards vary from British and US standards in a number of respects.

You mentioned this rifle had a scrubbed bolt I believe. Can you be sure the bolt is original to the conversion?

I would not use 7.62 Long Range Special Ball in this conversion, its chamber pressure exceeds the British MOD pressure limits for 7.62 rifle ammunition. That loading was not available while the L42 was in service and its unlikely to be suitable for use in rifles converted to specs in force during the 1970's and earlier. Its a Special purpose cartridge, not suited for many rifles.
There is no EpVat number for the Long Range Special ball and it exceeds the chamber pressure of all other US 7.62 Ammunition that does have an EpVat code number by at least ten percent.

Personally I'd consider the possible cracking or warping of a receiver due to firing a rain wetted cartridge to be a major flaw in a combat rifle.

I guess those canvas action covers paid for themselves many times over.

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In 1950 the material for rifle bodies (they made No.1 Mark 3* rifles; my addition) was altered from an EN steel to SWES 48 steel (not heat treated) except for the recoil shoulder and cam recess in the receiver. With this change the rifle receivers distorted when oiled proof cartridges were fired. This was discovered when hard and sometimes impossible bolt retraction was experienced. Large quantities of rifles were rejected. To avoid rejections the authorities ordered discontinuance of the oiled proof. Therefore from 1950 to the end of SMLE rifle production (June 1965) rifles made at Ishapore were proof tested with one dry proof only, although the specification called for both dry and oiled proof.

A bolt action rifle similar to the SMLE Mk. III*, modified to fire the 7.62 NATO cartridge was produced at Ishapore, first in February 1965. Their receivers were made of SWES 48 steel, un-heat-treated, and with the NATO proof cartridge receivers were found to distort with the oiled or the dry proof round! The material was changed to an EN steel so now the rifles stand up better to dry and oiled proof.

There's a lot you can read into what the author has said but I am not going to make any assumptions.

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I figure this solves the minor mystery of why some 2A rifles develop excessive headspace after only a few rounds of commercial .308 while others seem to have no problems.

US 7.62 Ball is loaded to 48,000 CUP which is within limitations of the action, but some commercial .308 is loaded to much higher pressures.

Alfred you are again in error on the pressure rating of 7.62 NATO ammunition, standard ball M-80 is rated at 50,000 CUP or 60,000 PSI (transducer method) average mean temperature

The .308 Win is rated at 52,000 CUP or 62,000 PSI (transducer method)
There is only 2000 psi difference between the .308 and 7.62

The 48,000 cup pressure you are using is for quality control checks in MIL-P-3984J done at 125degrees, minus 65 degrees and 70 degrees. The pressures listed for these tests are as follows”

48,000 CUP at minus 65 degrees
53,000 CUP at 70 degrees
55,000 CUP at 125 degrees

standard ball M-80 is rated at 50,000 CUP or 60,000 PSI (transducer method) average mean temperature ;)

The .308 Win and 7.62 NATO are for all practical purposes one in the same cartridge

https://www.milsurps.com/images/impo...08proof2-1.jpg
https://www.milsurps.com/images/impo...08proof3-1.jpg

"only 2,000 psi" doesn't sound like much till you take into account that these are Maximum pressures.
Besides which the Maximum Standard Deviation for the M118 Long Range Special Ball is 57,000 CUP.
How much farther does this exceed Maximum acceptable pressures?

Saying that its safe to fire loads that generate 62,000 psi in rifles like the 2A when some of these rifles could not even pass the standard proof testing for use with cartridges that generate pressures ten percent lower than that, and even the maximum acceptable levels for more modern NATO rifles is at a lesser pressure is unwise to begin with.
Add to that the Special Purpose rounds that can generate nearly a ten percent increase in that already beyond the pale pressure level and at the very least the best rifles will suffer increasing wear and damage and lesser rifles court disaster.

Theres already been one incident where a 2A owner was nearly castrated by a magazine blown out by escaping gas when he fired .308 ammunition in his rifle.

When a British Sniper reports the sort of failure to cycle of an Enfield action under the described combat conditions, a failure that might well have cost lives had not a alternative weapon been available, then its an indication that the ammunition and rifle combination has problems not easily detected by target shooters or police snipers in less arduous conditions.

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Originally Posted by Amatikulu

With all of the recent attention being paid on these forums to the Lee Enfield and proof pressures, I thought the following extract would be of value to some of you - I certainly don't want it to start another ruckus :thdown:

I have an awful lot of reference material and while reading today I came across a paper titled "Gun Proof in India - An Historical Account." It was written by Mr. A. G. Harrison the former Proof Master at the Rifle Factory Proof House, Ishapore, India and was published in "The Gun Digest, 33rd Edition, 1979."

I'll get it scanned later but for now I've extracted the part that interested me:

From 1908 to 1950 all military bolt action rifles made at Ishapore were proof tested with a dry proof round followed by an oiled proof round. The proof cartridge was loaded to 24 tons (2240lbs = 1 ton) psi breech presure, or 25% higher than the service pressure.

In 1950 the material for rifle bodies (they made No.1 Mark 3* rifles; my addition) was altered from an EN steel to SWES 48 steel (not heat treated) except for the recoil shoulder and cam recess in the receiver. With this change the rifle receivers distorted when oiled proof cartridges were fired. This was discovered when hard and sometimes impossible bolt retraction was experienced. Large quantities of rifles were rejected. To avoid rejections the authorities ordered discontinuance of the oiled proof. Therefore from 1950 to the end of SMLE rifle production (June 1965) rifles made at Ishapore were proof tested with one dry proof only, although the specification called for both dry and oiled proof.

A bolt action rifle similar to the SMLE Mk. III*, modified to fire the 7.62 NATO cartridge was produced at Ishapore, first in February 1965. Their receivers were made of SWES 48 steel, un-heat-treated, and with the NATO proof cartridge receivers were found to distort with the oiled or the dry proof round! The material was changed to an EN steel so now the rifles stand up better to dry and oiled proof.

There's a lot you can read into what the author has said but I am not going to make any assumptions.

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I read the article in the original publication when it first came out. I was stationed in Germany at the time. I discussed it with several German collectors and shooters and their opinon was that the article was 'sour grapes' from the author who was forced out by the Indian authorities. I've often wished that I had kept that article since then to refer to it. As I remember the final proofing was to fire 2 5 round chargers through the action and if it kept spec the rifle was issued. Ishapores were pretty thin on the ground until the later 80s so at the time it didn't seem to concern shooters in the U.S. except as a matter of academic interest.

I'm still a bit uncertain about the meaning of "EN" steel.
The European Normal Standards originated at about that time frame.

I've found else nothing on an EN prefix other than E stood for Electronic Arc Furnace Steel, but this was in reference to Stainless Steel Alloys.

High strength alloys were available in the early 20th century, alloys comparable with the strongest of todays alloys.
Heat Treatment can make or break an alloy.
The same alloy used for the brittle Low Number Springfield receivers when properly heat treated produced receivers among the strongest ever made.

I've seen enough damaged Enfields of all types that I know its not indestructable under combat conditions. I've seen enough Indian surplus No.1 rifles to know that many were much abused and saw little or no maintenance while in service.

Governments can't always be trusted to put the safety of the troops first. I'd remembered reading of instances where Enfield receiver proof testing quality and specifications had been compromised due to excessive failure rates, perhaps these were the origin of that.

EN stands for European Norm and is not a specific grade of steel as the EN covers the full range of steels. The author of the article was not sufficiently specific but we can take it that the steel type was changed to a less robust type.

Its possible that the Lithgow receivers that failed the conversion tests were made from a weaker alloy as well.
The rack full of Lithgows with damaged bolts but perfect bores I've mentioned before had dates in the late forties, when war time shortages may have been a problem.
The odd looking bolt head and extractor with Drill Rifle type coil spring that came with my Lithgow might have been a leftover spare from the conversion trials. It never ejected .303 cases properly but ejected empty mauser and 7.62 cases smartly.

I kept the action for possible sporter project in a less intense caliber, or for a .410 conversion.
The steel other than at the points induction hardened was deeply scored by a wire wheel so much so that the hardened areas looked like metal had been added there by welding and the surfaces recut.

The receiver serial number had also been restamped, the stamping so deep the numbers were unreadable and had raised edges like craters.
The track for cocking piece/sear is milled far off center.
This was at best a mismatched, out of spec, and suspect parts gun, not worth restoring, and I suspect not strong enough even for the .303 when new.

So you can see why I'm curious about the metalurgy used for the Enfields of various years and factories.

I was in the NRA office at Bisley on Saturday and on the notice board in large print Do Not use any heavier projectile than 144gn Nato round in No4 conversions damage will result. I think that advice would extend to the Indian 2a, 2a1 as well. That Indian proof load test is the same as the current proof test used in the UK test. One dry @+ 25% one oiled @ + 25%

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Originally Posted by Bindi2

I was in the NRA office at Bisley on Saturday and on the notice board in large print Do Not use any heavier projectile than 144gn Nato round in No4 conversions damage will result. I think that advice would extend to the Indian 2a, 2a1 as well. That Indian proof load test is the same as the current proof test used in the UK test. One dry @+ 25% one oiled @ + 25%

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Thats what I've been getting at all along. These Special purpose heavy ball rounds like M118 LRSB were not even in existence when the L42 and similar conversions were produced, they never intended the No.4 receivers to be used with cartridges that generate such high pressures.
The standard ball ammo is deliberately loaded below its maximum potential and far below the safe pressure levels of the M-14 and FN FAL type rifles so that in a pinch it can be used by other nations whose rifles were not as strong. The lower pressure also provided a safety margin and reduced wear on autoloader actions. 7.62 NATO Ball is not a hotrod cartridge, its basically a slightly updated equivalent of the 7.65 Mauser and .303 British, with lighter bullets for higher velocity.
The short case and OAL designed for more compact autoloader actions don't allow for hot loadings using heavy bullets without bullet bases extending into the powder space and sending pressures on an upward climb out of proportion to the energy gained.

A longer 175 grain bullet loading duplicating the .303 ballistics and using the same powder would have a higher pressure due to less room left in the case because the bullet must be seated to the short OAL.

There are Managed Recoil and Controled recoil .308 loads that generate low enough pressures that they should be safe in the 2A rifles, and many handloads that duplicate the 7.62 Ball at pressures within limits of the No.4 actions.