More Bad Press For The Enfield

[Surpmil]

Whose tune are we dancing to?

While as a layman I can't argue metallurgy with engineers, and the theories certainly sound convincing, where is the actual evidence in the form of failures?

It's now over 50 years since the last No4s were built (excepting Pakistan) and most of those in circulation are of WWII vintage, some have fired tens of thousands of rounds of 7.62mm since then. Have any blown up? Has anyone lost their sight or fingers from a No4 (or No1) blowing up due to metal fatigue from this theorized prolonged over-stressing?

Again, where is the evidence, or are we to believe that someday a No4 will fracture from protracted metal fatigue?

I'm inclined to think that "someday" would have arrived by now, if it is ever going to.

Of course we all know, or should know, how delighted certain groups would be, if they could condemn as unsafe the most common rifles in the British Commonwealth (yes, it does still exist! )

I really wonder if we should be playing into their hands?

Let them do their own testing and gather the "evidence" I say.

If this "metal fatigue" concept had any validity in this case, I think we can be sure it would have been dragged out by the NRA, instead of the highly tenous, contentious and contradictory stuff they've managed to assemble so far.

There's always email for the "theoretical discussions"

"Loose lips sink ships."

[slamfire1]

There is a margin of safety designed into actions, but because these are man portable, don't assume there is a lot of margin, because margin means weight.

I suspect that margin is why No 4 could be chambered in 308 Nato. I also suspect that no one ever assumed that these actions would be in continuous service for 60 years after date of conversion.

I don't have the material data nor the load data to base a stress analysis of the Lee Enfield, but I am going to assume that it was designed for an infinite cycle of standard pressure 303 cartridges. However the 308 cartridge operates at a higher pressure. Given enough cycles, it is reasonable to assume that it will fail structurally.

Now does the inclusion of water make it worse? Are the responses just denial or it is dangerous to shoot a Lee Enfield in the rain?

[jmoore]

"Fatigue" engineering really didn't get off the ground until the post WWII era. When they designed this action there were only basic notions of the whole design concept.

[slamfire1]

"Fatigue" engineering really didn't get off the ground until the post WWII era. When they designed this action there were only basic notions of the whole design concept.

Perhaps you are thinking of fatique, aluminum and the DeHavilland Comet? de Havilland Comet - Wikipedia, the free encyclopedia

Not being in school at the time I am not certain pre WWII design practices. However, I am looking at my 1941 edition of Modern Metallurgy for Engineers, on page 152 is a very nice S-N curve for carbon steels, and it is dated 1921. On page 153 is the relation of enruance limit to tensile strength and brinell hardness, and that is dated 1929.

At least for carbon steels, fatique lifetime was well defined and understood.

I don't know the design practices of British Small arms designers. They might have designed the bolt for a certain number of rounds in a 20 year lifetime and added a bit of margin. I would have designed the bolt for an infinite loading cycle, but that is me.

[Gnr527]

This is the subject of considerable discussion on several threads/forums and we seem to be burying ourselves under a welter of information!!

cant we take it one step at a time and take Alan and Surpmils advice and throw the ball back into 'their' court

'where is the actual evidence in the form of failures?'

[Surpmil]

There is a margin of safety designed into actions, but because these are man portable, don't assume there is a lot of margin, because margin means weight.

I suspect that margin is why No 4 could be chambered in 308 Nato. I also suspect that no one ever assumed that these actions would be in continuous service for 60 years after date of conversion.

I don't have the material data nor the load data to base a stress analysis of the Lee Enfield, but I am going to assume that it was designed for an infinite cycle of standard pressure 303 cartridges. However the 308 cartridge operates at a higher pressure. Given enough cycles, it is reasonable to assume that it will fail structurally.

Now does the inclusion of water make it worse? Are the responses just denial or it is dangerous to shoot a Lee Enfield in the rain?

1. The more tapered .303 case presumably puts more pressure on the bolt and receiver than the more parallel-sided 7.62mm case?

2. The commercial and military 7.62mm barrels are presumably built strongly enough to contain indefinitely(?), the pressures generated by the standard 7.62mm loading of their day*, without the support of the receiver ring they may be screwed into which obviously vary widely in strength? Is that not standard design practice? (*About the same as current loadings I assume?)

3. If that is the case, the strength of the receiver into which they are screwed is presumably not an important factor in containing, indefinitely(?) those pressures....

4....except of course the rearward pressure on the boltface and body and by extension on the body/receiver lugs.

5. So, we have 7.62mm barrels in No4s, built of superior steels to the wartime .303 barrels, often of larger dimensions (albeit outside the chamber area) and firing a cartridge that generates what, 15-20% more pressure than MkVII .303? How much of that "extra" pressure on the bolt is simply absorbed by the greater case adhesion in the more parallel sided 7.62mm case?

6. If as Ed says, considerably greater pressures are generated by reduced case adhesion, can we determine the numbers in these equations?

(I could be wildly off on some of this, so feel free to correct me - I'm just using what seem logical deductions to me!)

[ireload2]

>>>1. The more tapered .303 case presumably puts more pressure on the bolt and receiver than the more parallel-sided 7.62mm case?<<<

Why do you presume that?


>>>Next an action to slice up and measure cross sections<<<

This is not necessary.
Measure it with calipers. Where you have difficulty measure small rectangle and triangles and add their areas. It should take you a whopping 30 minutes.
If you have doubts measure to your best ability. Use an added 10% if you like. Use -10% too. The real number should fall between those values. This is not magic. It is engineering. Close counts like horseshoes, hand grenades and thermonuclear devices.

[jmoore]

I reckon having the best data available is rather better than guessing or making more assumptions than absolutely necessary. Plus, load paths aren't always at 90 degrees to the bore axis. I don't expect IMMEDIATE results here, but somebody's got to actually "get their hands dirty" and DO something!
Funding, of course, is always part of the situation, I understand we're not the "government" w/ "unlimited" resources.

But never mind me, I don't know nuttin'!

[ireload2]

>>>I reckon having the best data available is rather better than guessing or making more assumptions than absolutely necessary.<<<

You can't always wait until you have perfect information. It hurts nothing to write out the equation and plug in the numbers. If you don't like the answer double check your work.

[jmoore]

What I want to do is iniate a low cycle "fatigue" failure by rechambering a barreled action to either 300Win Mag or 300WSM. If that doesn't achieve the desired effect, then I think there's no point worrying about any 7.62x51 load.

Quick and fairly cheap. A remote firing test rig is no drama.