AIA #4 clone proofing

[ireload2]

The best materials for recievers out there are mild steels, that is steels with under 0.4% carbon content as you want the receiver to flex in the inner core, while having the hardened case to handle the loads without shearing.

For example the M14 line of rifles use 8620 steel, its a nickle-chromemoly steel, low carbon content (a mild steel) which is case hardened and in the M14 platform handles a life of 425,000 rounds.

Only tool steel I'd trust in a firearm other then 8620 is probably S7 or similar, as they are designed to be shock proof, running a piece of metal that is all the way through hardened can cause very large problems due to the shock loading that a firearm receives.
Dimitri

Earlier you posted that you might be interested in a Remington 700 custom shop rifle.
It is common knowledge that their receivers are made from 4140.
I believe that Ruger M77 bolts and receivers are cast from the same or a similar alloy. Care to elaborate on the contradiction with your statement above?

[ireload2]

I would be very concerned about the suggestion the receivers are all hardened steel... Hmmm... isn't there a lesson learned previously on the topic of receivers being too hard to the point of being brittle. What serial number early Springfields were they that were prone to cracking or shattering?

Maybe you might like to ask why the 700 Remington uses a through hardening steel for their receiver? This is not the early 1900s. A through hardening steel can be 32 RC or it can be 64 RC. Some can be heat treated almost anywhere in between.

[ireload2]

Because we are talking AIA rifles which claim to be military arms.
Dimitri

I don't think this is correct. I believe they are replicas just as an H&R Trapdoor is a replica.

[Alfred]

I looked up the applicable Mauser patents that the US paid a royalty for use of, and found that none of them had anything to do with the bolt, receiver, magazine ,or extractor, all three were improvements of the stripper clip.

DWM claimed that their cartridge patents covered the design of the .30/06 cartridge. I suppose the rimless case and spire point.

International patent protections were still a murky issue back then. To be sure of protection you'd have to file a patent in several jurisdictions covered by international agreements.

Near as I can tell Enfield receivers are hardened to some extent, more like a sword blade , and the locking surfaces are given an extra hardening process.

The thread on Indian proof testing tells of a substitution of a non hardened steel that resulted in failures during proof firing.

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.

The low number Springfield receivers didn't fail because of the type of hardening, but rather due to poor execution of the forging and hardening process. They did not intended that the receivers be hardened to the same extent all the way through. Overheating of the steel resulted in many receivers being brittle.

[Son]

Maybe you might like to ask why the 700 Remington uses a through hardening steel for their receiver? This is not the early 1900s. A through hardening steel can be 32 RC or it can be 64 RC. Some can be heat treated almost anywhere in between.

Ok, I don't know why they use the steel they do... but I know why it doesn't matter a toss if they use kryptonite, cast iron or even cardboard.

The pressure bearing components- the bolt and the chamber- are locked together at the time of firing, so there is no force imparted onto the receiver at all other than the effect of recoil as it is transferred to the shooter's shoulder. Totally different for a rear locking action for example... Lee Enfield... where the pressure is restrained by the receiver from near the rear of the action where the bolt locks to the rear of the barrel where it is screwed into the action.

There are probably more firearms out there that use die cast aluminium or thin pressed mild steel sheet for their receivers than harder grades of forged steel. Maybe the Remington uses it to maintain high grade surface finishes and tight tolerences between moving parts- lengthening their servicable life and making them look pretty... nothing to do with controlling the chamber pressures.

AIA were very clever using a description like they do. It's put together to make people who have doubts about a real Lee Enfield taking full pressure 7.62 loads (and the associated stigma with rear lockers) feel better about their product... All they really did by enlarging the dimensions slightly and use of "milspec grade alloy" (gotta take your hat off to thier spin doctor!) was make it easier to machine and remove the need for heat treatment hardening of load bearing surfaces. DOUBLE WIN for them- cheaper to make with less skills required.

[Alfred]

I still haven't found any information on the exact alloy of steel used for Enfield Lock receivers.
I figure it just about had to be at least a mild Nickel Steel, nickel steel has excellent elastic properties and would be the best choice for a rear locking action. Its best that such a receiver strecht just a hair and snap back, probably less than one ten thousandth of an inch under a normal load.

Breaking strength of the earlier LE receivers was quoted by Ross as being 85,000 Pounds, but he didn't say if this was a test to destruction cartridge or whether the figure was from a mechanical or hydraulic application of force. I'm figuring hydralic testing, not sure why but that would fit in with some things I've read of 19th century methods in testing of such metal structures, especially ordnance breech mechanisms.

Considering the power of main battle cartridges of the period and up till post WW2 times, the actions of every sucessful bolt action rifle were remarkably lightweight.
The No.5 always seemed an odd duck to me, they couldn't have saved much weight from lightening the receiver, lighter wood or a composite stock and slimmer barrel would have done much more without weakening the receiver.

[Dimitri]

Care to elaborate on the contradiction with your statement above?

No its not, 4140 is heat treated the same way as the 8620. You first "through" harden the steel, but due to the low carbon content (0.40% hence the 4140) case harden the outside for a tough durable surface.

The inner core of 4140 once supposedly through hardened gives you a core of 35-40 Rockwell "C" scale, getting it to 45 or higher is practically impossible. Instead the core is heat treated to make it tougher but still retain elasticity, cause without that, the receiver will want to shatter instead of flex under the pressure of the fired round. Then the surface is hardened though "case hardening" which can be done with plain Carbon packing, Nitrogen based methods or a few other methods, to give you a hard outer shell of 55-65 Rockwell C to allow the receiver to last with little wear and tear from repeated firings.

Maybe you might like to ask why the 700 Remington uses a through hardening steel for their receiver?

They don't. Read my reply above. Through hardened steels are actually tool steels, with a high 0.50-0.95% carbon content that will allow the heat treatment into the core. All other steels will not do that 4140 is still just a mild steel.

Dimitri

[harry mac]

They'd only pass Birmingham proof if they were exported to England, and that still is not a good judgment of function without it being checked for microscopic cracks.
Dimitri

That's exactly my point. They have been exported to The UK and are up to UK proof standards. If the rifles are strong enough to pass UK proof then there is no issue with their strength. As far as I'm aware UK proof standards are more stringent than SAAMI.

[Dimitri]

If the rifles are strong enough to pass UK proof then there is no issue with their strength.

That is where your wrong, a proof load can be passed with a rifle of questionable manufacture that would not hold up after repeated firings.

Its like a weight lifter, a weight lifter can max out with 500 pounds and do it a couple of times without showing signs of not being able to, just as a rifle can handle a couple of proof loads, but when that same weight lifter does sets, he may only be able to do 250 pounds 15 times before having to stop.

Metal fatigue is the issue, not necessarily the rifle passing the proof testing. Especially when materials of questionable origin are used. Most military and commercial arms continue to use the same few materials as they always have because the arms designers know they work and will hold up in the long term with little to no metal fatigue from repeated firings, as well as can handle the pressures generated with proof loads.

Dimitri

[tiriaq]

As far as the amount of flex in a Lee Enfield action is concerned, I suspect it is a lot more than a ten thousandth. Set up a rifle with minimum headspace, neck size to substantially reduce fireforming, and cases will still have a shorter lifespan than if used in a front locking rifle.
Cases stretch in a Remington 788 rifle because of bolt compression, not receiver flex.
But rear locking actions do have characteristics not observed in front locking ones.
A Remington 700 receiver is heat treated, but I've not seen one that was "through hardened" or carburized. They can be drilled or machined without difficulty - for sight mounting holes, blueprinting, etc.
The AIA rifles obviously withstand industry standard or proofhouse testing. Prooftesting does not mean that a firearm will not fail at a later date.
Many owners report them to be perfectly satisfactory rifles.
Everyone's cup of tea? Obviously not. Certainly the product of a rather atypical company. Long term future? Who knows?