More Bad Press For The Enfield

[303TF]

Well written , or is that spoken ?

Information

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[Patrick Chadwick]

Gentlemen, I have been following this thread most carefully, and I thoroughly agree that if one is to fight successfully against half-truths, one needs the whole truth. And there is a lot of unnecessary correspondence generated by imprecise documentation (for instance, I have never seen an official drawing of the 303 chamber and cartridge, with maximum and minimum tolerances, as as must have been used for manufacturing Enfield Rifles).

There is, however, one major difficulty in the dimensional discussion in that the CIP dimensions are all in metric units, and correspondents/NRA are happily quoting inch dimensions that do not seem to match the CIP mm dimensions. I do not claim to be in possession of the truth, but I do take the trouble to present sources that other correspondents can check. Any CIP figures quoted in the following are published values, taken from the RUAG Ammotec reloading manual, are included in German legislation, and match CIP data. I am aware that there may be other values to which I do not have access. If others have such figures they should please publish them with proper authentication (i.e source reference or copy of original data sheet or drawing):

The relevant example for this discussion is the so-called throat diameter. So-called, because the throat is not a point, but more properly a transition cone that starts (typically) just in front of the cartridge mouth and ends where the full rifling depth has been developed.

CIP data sheets do not use the word throat, but define the diameter at the "Commencement of Rifling", and I think this is what correspondents mean when they refer to throat diameter. CIP also defines the transition cone angle and the length of the cone, but in chamberings with a pronounced freebore it is often not clear where this diameter is actually measured. As a result, I have sometimes found it difficult to reconcile the diameter, length and angle figures. To be fair to CIP, these diameters are footnoted as "Check for safety reasons". And, basically, cartridge diameters are given as MAXIMUM and chamber diameters as MIMIMUM. A most unsatisfactory state of affairs from an enginneering viewpoint, as I have not yet discovered any tolerances, apart from the dubious "delta L".

Reference has been made to "the throat diameter is less than the CIP specification of 0.311” but not smaller than 0.3085”. With regard to the above, I doubt there is such a specification value. The CIP dimension for "Commencement of Rifllng" is given as 7.87 mm MINIMUM. As the inch has been defined for decades as 25.4 mm PRECISELY, this converts to 0.3098425"
It is reasonable to approximate this to 0.0310, but not 0.311” or 0.3085”. So please, where do those figures come from?

I apologize if this all seems a bit picky, but it is just engineering nonsense to produce figures out of a hat and then construct safety-relevant arguments from them.

In particular, a "Commencement of Rifllng" diameter of LESS than 0.310" (or 0.3098", if you can really measure it) would be UNSAFE in ANY type of .308 Win rifle. Like the DP blow-up analyzed by Peter Laidler, it seems that there are axe-grinders at work here who are determined to force false conclusions.

Summarizing: I am unable to find a source for the figures quoted by the NRA. Expressing it non-scientifically, they should put up or shut up.

Patrick

[slamfire1]

Conversions retaining their original Enfield barrel or a replacement barrel as manufactured by RSAF Enfield are safe to use with commercial CIP approved ammunition, which complies with a MAWP of 4150 bar, loaded with any weight of bullet, providing they carry a valid proof mark, and are still in the same condition as when submitted for proof.

4150 bar = 60K psia

Conversions which have been checked and found to comply with Rule 150 may safely be used with any ammunition supplied by the NRA including the 155 grain Radway Green Cartridge, 155 grain RUAG Cartridge or any other commercial CIP Approved cartridges loaded with bullets of any weight provided that the ammunition pressure does not exceed 3650 Bar when measured in a CIP standard barrel”.

3560 bar = 53K psai

I don’t see supporting design information on the No 4 actions. These actions were designed to carry the load of a 303 British cartridge, plus a safety margin.

What are the maximum and min pressures for a 303 Brit?

Anyone know whether the designers calculated 303 bolt load based on rim size, or the internal diameter of the case?

[Edward Horton]

Slamfire1 and forum members

The .303 Enfield is stamped with 18.5 Ton or 18.5 tsi which equals approximately 37,740 CUP or copper units pressure by American testing standards. Because the British used a different method of proofing with oiled proof cartridges and the base crusher method the pressure readings are different than American standards.

To convert the British pressure figures to American testing standards you must add approximately 20%

.303 British 18.5 = 37,740 CUP + 20% = 45,288 CUP (18 or 18.5????)

The normal rated .303 chamber pressure is 45,000 CUP or 49,000 PSI.

The 19 tsi for the 7.62 No.4 Enfields equals 19 x 2040 = 38,760 + 20% = 46,512 and “below” the 50,000 CUP or 60,000 PSI transducer method rating of the 7.62 NATO cartridge. (This might be why they are requesting the rifles be re-proofed) What is needed is more information on the older testing methods and procedures to know where we stand.

What is needed now is the actual pressure rating written in Tons or tsi for the proof pressure testing cartridge for the 7.62 under the older proof methods. This is because the British military used oil proof rounds to test their small arms and a oil round delivers twice the force to the bolt and action than the present dry CIP cartridge method.

If someone would furnish the older data on what the tsi rating was for a 7.62 proofing round, a correlation between the old and new pressures of proof testing could be made. Again the British military proofing standards exceed present day civilian CIP standards and CIP does not use oiled proofing cartridges.

Again 19 tsi only equals 45,512 CUP BUT there are conflicting tsi figures being written to add further to this or my confusion on WHAT were the actual pressures. Please read below (19.07tsi to 20.71 tsi for the .303 and 22.3 tsi for the 7.62 NATO???) Normal operating pressure and NOT proof pressure.

[Alan de Enfield]

Slamfire1 and forum members

The 19 tsi for the 7.62 No.4 Enfields equals 19 x 2040 = 38,760 + 20% = 46,512 .

.

Ed - a slight mathematical error
A ton is 2240 lbs (and not 2040), so 19 X 2240 + 20% = 51072

[Steve H. in N.Y.]

.....

[Edward Horton]

Ed - a slight mathematical error
A ton is 2240 lbs (and not 2040), so 19 X 2240 + 20% = 51072

Alan de Enfield

It was more than a “slight mathematical error”, it was Alzheimer's plus my two dyslexic typing fingers tripping over each other.

Thank you for clearing up my mistake. (I kept scratching my head wondering WHY the pressure figure didn’t match the tsi figure)

[Patrick Chadwick]

3650 bar is the Pmax as per CIP for a .303 chambering.
4150 bar is the Pmax as per CIP for a .308 WIN chambering.

Patrick

[ireload2]

>>>This is because the British military used oil proof rounds to test their small arms and a oil round delivers twice the force to the bolt and action than the present dry CIP cartridge method.<<<

Not according to the laws of physics.

[jmoore]

All right you people, so who over in England is going to run a 300 Winchester Magnum reamer into either a barrel and screw it onto a No.4 action that's well used? Then see how long it lasts. Do Dye Penetrant exams of the bare receiver and bolt every 10 round for the first 100 and every 100 for the first 1000 rounds. Really!

I've broken out some books looking at "fatigue life" including:

The American Society for Metals- "Metals Handbook" Vol. 1 Properties and Selections of Metals 8th Ed. (yah, its a little old) Chapter on "The Seletion of Steel for Fatgue Resistance" seems pertinent.

"Large Fatigue Testing Machine and Their Result-1957" An excellent early publication by the American Society for Testing and Materials

"Symposium on Fatgue of Aircraft Structures-1962" also ASTM

Looking for my 1963 publication that's the most useful- I've carefully put it in a safe place that I can't remember...

So, now I could use material and heat treat specs for the No.4 to make cross ref to US specs.

Next an action to slice up and measure cross sections- got plenty of SMLE actions spare, but no No.4s.



BTW, I think further proofing requirements would be a miserable idea on existing weapons, its only to show that there's GROSS faults w/ the weapon as constructed, not a periodic "safety" tool! As these actions are not failing in a few cycles (less than 100 to 1000), "Microcracking" or "fatigue" is the suspected culprit. Small cracks may be easily found using NDT procedures such as "dye penetrant" or "magnetic particle" testing. These procedures DON'T harm the weapon and WILL show any dramas if performed by trained individuals.


We might try and round up a reamer here and set up a test rig, but it won't help ya'll over there...