SMLE materials specifications

During the, somewhat undignified at times, discussion about the strength of L E actions, someone asked about the materials used in manufacture.

Well, which bit do you want to know about?

I have in front of me a document called:

Specification No S.A./462 P, being for Rifle's No1 Mklll, with bantam long, normal and short butt (S.M.L.E., .303-in. With cut-off.)

Refers to 57/Spefns/3866 Approved 14. 12. 1938

Received by somebody careless on 19 JUN 1939

And it says:

Body -- Steel. B.S.S.5005/401 -- Partially oil hardened, tempered and browned.

Barrel -- Steel. D.D.8 -- (Heat treated)

Bolt, Breech -- Steel. D.D.8 -- Oil-hardened, tempered, polished and browned or oil-blacked.

Head, breech bolt -- Steel B.S.S.5005/103 -- Case hardened and polished

Further, on page 8 it states: "If the bolt-head be made of mild steel it is to be marked with the letter "M" on the top of the wing."

NOTE: earlier specifications (S.A./242 for Rifle, Short, Magazine, Lee-Enfield (Mark 1). |C.|) 13th July 1903, called for the bolt-head to be made from malleable cast-iron, specifically 34F Special gun iron, case hardened.

Regarding barrel proof, refer to page 12:
(g) Proof. - The barrel will be submitted with the action attached for proof. The distance from end of bolt to face of barrel will be tested with a cartridge head gauge .067-inch. The proof will then be carried out with a proof cartridge, the charge being about 33 grains of No.3 cordite, having a service bullet of 215 grains, giving a mean pressure not below 24 tons per square inch, after which the action will be examined; and the barrel, body, and bolt head will be marked with the proof mark."

I have started doing a scan and OCR on these documents. The originals are wax-stencil prints on foolscap size paper. The long tables are probably going to give me the horrors. Happy to bung them into the "library" on completion.

FWIW, 24 British tons per square inch is 53,760 psi.

Jim

I wonder if there was a general replacement of the cast iron bolt heads or if they were removed from service on an as required basis.

Thank you for posting the information--it is interesting but incomplete if anyone was asked to duplicate any of those parts.

As an engineer, I would need to know what testing was required to prove out the design. Heat treat without temperatures and times for annealing and final heat treat are missing. The call outs are equivalent to baking a cake and saying that to make it you use flour and eggs with no further information.

Comparing British and American period material descriptions is a fascinating endeavor. Britain was willing to define and purchase material from suppliers based on the suppliers name for the product. The effect was to lock in that material with the part, handicapping others from quoting the business. In contrast, the US requires full explaination of components, per centage of components and details of processing along with appropriate testing to insure part performance. In the US any supplier can buy a steel made to SAE standards from any steel mill. Heat treat requirements would also be set up in a set specification that any heat treat shot can follow. In the automotive business, any part going on a car had to meet established engineering specifications, material and testing, before being released for production. Any company given this information would be able to quote the part.

Rolls Royce jet engine material specs. continued that legacy. Often the information you needed for processing parts were hidden away in a completely different document that contained what you really needed to know! Within said document there would be references to other documents or standards. It made sense to the original designer/engineer who had that stuff at his fingertips (or was in the old brainpan!), but to the poor mechanic fabbing up parts 20 years later and separated by a common language, Aieeeeee! RB211's were fantastic engines, but sometimes you just wanted to give the whole RR design department a good thrashing.

Anyway, with futher documentation, things ought to clear up.

Yes there is that problem about what a material actually is. In an annexe to Specification No.S.A./242 for the MK1 SMLE, 13th. July 1903, there are descriptions of various materials.

For example:

""Iron, Gun, Special"

The iron must be clean, ((free from all impurities (struck out)) and free from small "greys". as the slightest imperfection shows irself when the material is polished and case hardened.

The ultimate tensile strength per square inch must not be less than 22 tons, with a minimum permanent elongation of 12 per cent. and a minimum contraction of area at point of fracture of 45 per cent.

The material for the screws, butt plate, must be cold drawn."

(Not much to go on there!!)

This material is specified for:

Bolt head,
Bolt head charger guide (remember, this is a Mk1 SMLE)
Bolt, stock
Washer, stock bolt.



However, the bolt body is to be made from Steel, 56A 42.

"Specification O.F., 56A 42

To be cast steel, free from seams and flaws, to harden in oil, and temper suitably for these components.

An analysis of the steel should show a composition as follows:-

Carbon ... ... ... from 0.67 to 0.77 per cent.
Silicon ... ... ... " " 0.15 " 0.25 " "
Manganese ... ... " " 0.80 " 1.00 " "
Phosphorus ... ... not to exceed 0.04 " "
Sulphur ... ... ... " " " 0.04 " "
Copper and other impurities, only traces.

To contain no special ingredient such as chromium, nickel, etc. without intimation of their presence.

Standard test pieces, four inches long, will be made from various bars selected indiscreiminately.

The result of such test to be as follows:-

Yield point per square inch ... ... not below 26 tons.
Ultimate stress per square inch ... " " 55 "
Extension per cent. in four inches ... " " 11
Contraction at area per cent. ... ... " " 20

All steel employed in fulfilling this specification must be manufactured from Swedish or other high class approved ores only.

56A 42 was also used for:
Aperture sight
Barleycorn, foresights
Catch, magazine
Cocking piece
Locking bolt
Locking bolt safety catch
Sight, back, slide catch
Trigger

The 1921 drawing for the bolt head refers to a specification document, S.A./1117 B, R.S.A.F. 3095(1) which, unfortunately, I do not have.

The drawing has a number of interesting details:

1. The rear of the threaded portion still shows the notch for the early type striker as opposed to the later and better known "Striker B".

2. The material is simply noted as being "wrought iron, or mild steel, case hardened and polished"

3. Referring to the qualified 20 TPI threaded section: "NOTE! For spares - Qualify between 9deg and 13deg in advance of new component".

There are components and components, obviously.

Not only all that, but in the good old days, before fancy pyrometers and other nifty toys, "Cherry red" on a heat treatment specification could be quite different between day shift on a sunny day and the night shift or on a heavily overcast day. And doing this work under war time duress could easily account for such nasties as the "burnt" and extremely brittle cocking pieces occasionally found on No4 rifles, amongst other things.

Yup, heat treat methodology really improved starting WWII, much of it originating in aviation where a large "factor of safety (or stupid)" could not be tolerated.

I do have (still, I think) a small bag of broken bolt heads that are snapped off right at the threaded portion that are surely cast iron. Brittle fractures all! Not my fault, I didn't do it, wasn't there!

Does the price determine the quality of the 'ore?:dunno::nono:

Sorry gents. Couldn't resist:D

Think I rooted out B.S.S. 5005/401 (The receiver body material as listed in 1938):

5005/401

Fe
; Ni, 2.75-3.50
; Mn, 0.35-0.75
; C, 0.25-0.35
; Cr, >0.30
; Si, >0.30
; S, >0.05
; P, >0.05

From this document (Warning! Its fairly large):

ftp://166.111.30.161/pub/2.%E9%BC%AE.../44927_41b.pdf

pg#388 out of "Tables of Alloy Classes"

Just a wee bit more info. Will look more later. ETA: Having difficulties digging deeper into this document- there's supposed to be refs on pgs 471, 472, 600

This disinclination to reveal what would now be called the Technical Data Package, on the ground that it contained proprietary information was not confined to British firms. Winchester and Remington were driven crazy trying to work out how to make .45s from the limited information Colt gave them. Much of it existed only in the foreman's workbook, or in his head.