Abandoned test of Australian #1s.

[Bruce_in_Oz]

Just to add a little more to Thunderbox's posting- the trials were conducted in 1958. The request was made by the RAAF for Lithgow to attempt to convert existing rifles to the NATO round for airfield defence use. They ended up being a hybrid between the No6 (the dozen built for the test were made from existing No6 rifles) and the SLR (which was already in production at Lithgow) supplying the rest of the parts.
Read between the lines- the RAAF bean counters didn't want to spend their allowance on new SLR's, but had to comply with the new NATO standard round. The factory chucked a few together, blew some up in testing, and sold SLR's to the RAAF.

As I started this, I would like to thank Son for his addition of the RAAF bit. My points about logistics and professional pride were intended to refer to the oft-times bizarre machinations of defence procurement. What "modern" defence force wants to be seen in public with recycled antiques, regardless of quality or performance? Think about the weird history of the L4 in Oz service. What shiny-arsed public servant wants to spend his own?? money on new toys for those grubby, foul-mouthed diggers?

Remember that all this took place in the '50s, and in some way is parallel to the M-14 saga. Remember the M-14 and its "support/LMG version. Then think "L1A1, L2A1". Skip a couple of years: add M-60, a few more years, M-16. Then think L-85 and variants.

However, all this is a long way from the original discussion about the structural integrity of Lee-Enfield actions when firing other than good old .303 ammo.

One thing that cannot recall being discussed in detail was the issue of chamber dimensions. There is, to my knowledge, no such thing as a "standard" 7.62 NATO chamber, nor is there a "standard" 5.56 NATO chamber. There is a headspace datum for both, however, I can read from the numbers on engineering drawings, that the chambers for M-14, L1A1 and M-60 are NOT identical and a SAAMI spec .308Win. chamber is different again, especially around the neck and throat. Similar story for M-16A2, M-4 and Minimi in its various incarnations and .223 Rem.

Why? Because the interaction between the body, neck and projectile in all barrels and actions using the cartridge is not the same in all cases. Factors of port pressure, system dwell time, initial opening speed, existence (or not) of primary extraction'''etc., etc., etc.....For example, my information (from a factory rep.) is that it took the FN folk quite a few goes at the chamber and throat of the Minimi barrel to get the gun working reasonably well with NATO STANDARD ammo.

As near as I can work out, SMLE barrels are throated to accept ALL issue .303 ammo. Therefore, they are throated to accept Mk6 ammo (Leade of 0.60") because Mk6 and Mk7 existed in parallel in the ordnance system for quite a while, especially during WW1. Would they have shot Mk7 "better" with a shorter leade? Possibly. Would there have been "issues" if the only ammo available for combat was Mk6 and the barrels were in relatively good shape? Very likely.

Do not know about No4 barrels as I am still trying to find someone with a proper drawing for one.

[tiriaq]

Does the "SC" mark on SMLE barrels not refer to "Short Cone", the throat arrangement for Mk. VII as opposed to Mk. VI ammunition?

[Bruce_in_Oz]

tiriaq,

Well spotted.

On page 576 of Ian Skennerton's latest tome, "The Lee-Enfield", there is a reference to "S.C." stamped on the barrel, behind the rear sight. According to the text, it means "Small cone increased; lead from chamber to rifling for MkVll ball". The exact meaning and history of this marking is not explained

I am a little unsure about all this. My SMLE barrel drawing post-dates Mk6 ammo by a good deal. I may have a lead, so to speak, on a barrel drawing for a Lee Enfield Mk1 barrel, but not getting too excited until I see it in daylight.

However, 0.600" leade looks right for Mk6 ammo, given the amount of projectile forward of the case; 0.827" of a total length of 1.25", according to "Textbook of Small Arms, 1904". It would allow quite a bit of free-bore for Mk7 ammo. At that distance from the neck, the Mk7 bullet is about 0.178" diameter. The ogive is such that bullet diameter is down to 0.303" at approx. 0.200 " from the front of the case. As I sold most of my cartridge collection some years ago, I cannot find a Mk6 to measure, nor have I yet found dimensioned drawings for the projectile. Can anyone else help?

[Bruce_in_Oz]

But wait, there's more!

This is the good bit about ferreting through documentation.

Re. "S.C." on the barrel: the complete description, ex an extract from an unidentified (header information missing and footer illegible) instruction reads thusly:

"Small cone of chamber enlarged .002-in."

As I understand it, the "small cone" is the short cone between the cartridge neck portion of the chamber and the leade. If it were only enlarged .002" in either length or mean diameter, then it would make little difference to the accommodation of projectiles. I suspect it is more to do with "crud" clearance and allowance for variable brass length.

Anyway, the saga continues.

[Son]

As soon as I get a chance, I'll pull down a MkVI round, empty and de-cap it, then re-fit the projectile and fiddle with the OAL untill it engraves in the rifling. Should be an interesting exercise- just need the time to play...

[Surpmil]

A friend of mine who is a very competent gunsmith and competitive shooter told me that he once saw a 7.62mm No4 crack/shear the smaller of the two lugs on the bolt due to wet rounds; it was a VERY rainy day he said. The user was in no danger as the long lug could never crack/shear; he simply had to change rifles, and later, a bolt.

Didn't put my friend off, and wouldn't put me off! He has probably re-barreled dozens of No4s and must have shot 100,000+ rounds through them easily in all winds and weathers.

Such things happen occasionally, even with rifles produced in peacetime by 'trained' employees; not surprising it should happen occasionally with rifles produced 30+ years before under the pressures of wartime by men and women who in most cases had probably never seen a rifle a few years before.

Early Eddystone P14s, late 03 Springfields, Rosses...they've all had their problems. Still fine and historic rifles for the most part.

With a record like the Enfield's, I regard the rifle as immune to "the slings and arrows of outraged" competitors. That being the case, we 'devotees' can afford to be equally so.

C'etait la guerre!

[Thunderbox]

.... due to wet rounds; it was a VERY rainy day he said.

If it cracked and sheared off, then it would have been the end result of a very long process of some sort of fatigue cracking, and not directly caused by one shot with a wet round.

- ALL Enfield Rifles (in UK service at least!) will have shot frequently in the rain with wet ammunition. The magazine even has a drain hole supplied;

- it was routine for soldiers throughout the entire Enfield era to clean and oil ammunition as part of their battle prep. Hence nearly all service rifles have also fired plenty of rounds with at least some oil on them;

- extensive trials were held to see if oiled ammo could be used to accurise rifles. One observation of these trials was that oil (and, presumably, water) was - during the firing and expansion of the cartridge - was simply squeezed forward into the area of the rifling lead. By implication, there wouldn't much remaining to prevent chamber wall adhesion;

I think people are still making a massive mountain out of a tiny molehill with regard to the oil/water on ammo thing, and choosing to ignore the rather obvious empirical evidence - millions of rifles that have survived decades of hard use with no ill effect other than minor mechanical wear from hundreds of thousands of bolt cycles.

[Surpmil]

Yes, and it occurs to me that it might have been a non-original bolt that was not properly lapped in either, so that too much of the load went on the smaller lug. There was quite a lot of bolt-swapping among the target shooting crowd. One sometimes sees Long Branch 7.62mm conversions with replacement bolts that have matching conversion numbers but mismatching 'original' serial numbers. Reportedly if the bolt provided with the rifle did not pass the hardness or magnaflux tests another would be fitted that did. Though I would expect it would be lapped in, in the Long Branch case.