Hello Guys

My smith and I are debating lug strength for a design we are playing with. We have used the methodology and numbers provided by Dan Lilja on his website. These numbers will in due course be checked by an engineer.

We are still trying to reduce the shear area (and size) of the lugs and are wondering if we should be considering other than Pre-Hardened 4140 at approximately 26-32 RC to gain improved yield strength.

Are there any high yield strength steels with good machining characteristics that don’t require post machining heat treatment that we should be considering ? Will any of these take conventional bluing ?

Thanks - Foster

You might look at the ETD-180 steels with a Tensile of 180,000 PSI

Also the 17-4 PH stainless is something to consider.

I doubt that you will be successful in producing a bolt adequate to the task without post HT

If you change your mind I'd suggest 8620 and case harden after manufacture.

Tentman

There are some very exotic American Boutique steels which are readily available and suitable to your application. I can supply you with specification and sources for purchase.

Send a PM if you are interested.

If you were to use 4340 and boost up the hardness to 40 HRc you would get ~ 180,000 psi but it would be a bit more difficult to machine.

4340 is diffinitly a better steel , but as mete said difficult to machin due to Nickel content of steel.
yes

I have been making things from the pre hardened 4140 RC28 through J&L
http://www.jlindustrial.com/MXP-60521H/SEARCH:KEYWORD/product.html

It is way too easy to machine in the trade off between strength and machinability.

My father, the gun designer, designed some recoil springs from 4140. He called out the hardness "closed and ground" etc, but no force. I asked about that and he said that would be double dimensioning. That information is inherent in the size, shape, and hardness.

What does it all mean?
4140 can get allot stronger than RC28.



http://images.google.com/imgres?imgurl=http://www.varmi...1%26hl%3Den%26sa%3DN




Rifle Bolt of 4140 steel heat treated to a hardness of 43-45 Rc

Hardness and machineability are concerns depending on wthe application. Toughness and stability ar more important in critical high pressure applications where an "explosion" is involved. There are many types of both 4140 and 4340. The specifications vary widely. There are much better steels than these when something tougher is needed.

Per the October 16, 2000 issue of "Design Magazine", Ruger had a problem
with the 454 Super Redhawk design.
The 410 stainless in prototypes was ok with the 65 kpsi working pressure of the 454, but not ok with the 93.5 psi proof loads.
The original Super Redhawk had been designed for the 36 kpsi 44 magnum.
Making a six shot, a design goal, was made difficult by the 454 larger cylinder holes AND larger proof pressures.

The Cylinder solution was to go to a specialty stainless, Carpenter's Custom 465, a martensitic alloy with an ultimate tensile strength of 260ksi at peak aging.

Also the barrel had a problem. The standard 410 stainless was ruled out because of "throat slamming", a gas erosion problem. The first solution
was 15Cr-5Ni stainless steel (15-5), but it took 28 minutes to machine instead of 17 minutes like the 410. Ultimately Ruger chose Project 7000,
a 15Cr-5Ni type stainless designed specifically for machinablity. It matched the 410 machine time.

What about the Niagra LaSalle Steel Co. 'Stress Proof' & 'Fatigue Proof' steels? Aren't they designed to hand the explosion and resultant vibration & pressure spikes that an action has to handle?

FWIW - The Holland & Holland site reports that they use SAE4340 for their rifles & shot guns.

Very interested in hearing peoples thoughts on this...

Niagra LaSalle

Best Regards,
Dave

Tentman - PM inbound with specifications and links.

Thanks Macifej (and others). I am still checking the various references. We were trying to avoid post machining heat treatment so as to minimise warpage etc. However as always there are many ways to skin the cat. Am I reading you all correctly that the martensitic alloys with their simple and low temperature heat treatment may be the way to go ? It would be really good to get into the 180,000 psi yeild range if we could . . . now getting there in something that could also be blued, now that would be really great. So maybe its back to 4140 or 4340, take a different approach to tolerances and accept some post heat treatment "adjustments"

Thanks - Foster

Some steels distort much less than others when heat treated. One such material is A-2 which is air hardening tool steel.