Gun Proof in India - An Historical Account

[Alfred]

"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.

[smle-man]

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

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.

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.

[Alfred]

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.

[Amatikulu]

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.

[Alfred]

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.

[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%

[Alfred]

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%

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.