An Engineer's take on S&W.

[j38]

Fascinating subject and write-up. Thanks,

Jerry

 

[perpster]

Very interesting. I wonder what his thougts are on scandium and titanium alloys used by S&W.

 

[jack the toad]

Very interesting. I wonder what his thougts are on scandium and titanium alloys used by S&W.

+1 Me too

 

[tekarra]

An informative post indeed. To me, the significant comment is that American metallurgy reached its peak in the 60s. The evolution of metallurgy has accelerated since then, sadly most developments have been overseas.

 

[sw282]

siiiiiiiiiiiiiiiiiiiiiiiiii

 

[Catshooter]

Very interesting and informative.

I too would like his input regarding Scandium frames and the two-piece barrels in use today.


Cat

 

[Dave T]

I originally posted this here (Hand Ejectors) because of the info contained about 1950s materials and machining. This latest e-mail is probably better suited to the more modern era but several here asked about scandium so I'll continue to post here. I asked in the context of S&Ws light weight 1911s as the original alloy Commander was my favorite off duty and plain clothes weapon. I cracked 3 Commander frames just shooting them so I wanted to know if adding scandium to aluminum would make a more durable Commander. Here is my friend's response:


"I did some research into the properties of aluminum-scandium alloys over the weekend. I quickly learned, as stated in one journal article, that "information on the properties of aluminum-scandium alloys is scanty." Further, many of the aluminum-scandium alloys are proprietary, which means that information on composition is not available. Usually properties of proprietary materials are provided by the manufacturer, rather than a neutral third party, and must be cautiously evaluated. Finally, S&W does not specify what aluminum-scandium alloys are used in its products. So there is some room for differences in opinion regarding the suitability of aluminum-scandium alloys in firearms.

One paper did show an improvement in both ultimate tensile and yield strength for a 7010-T6 aluminum alloy after addition of scandium. Ultimate tensile increased about 7%, and yield strength about 4%. This increase is in keeping with the patent claims on the alloying of aluminum with scandium. Easton, one of the companies offering aluminum-scandium bicycle frames, does not claim any increase in strength with its aluminum-scandium alloys in comparison with conventional materials.

However, tensile and yield strength are not the only properties of importance. Even more important in determining service life is the fatigue strength of the material. Unlike steels, aluminum alloys do not have an endurance limit at which the lifetime is indefinite. Typically fatigue is evaluated by a combination of factors such as allowable strength for a given number of cycles and fracture toughness. Typical fatigue strengths for aluminum alloys with 0.25 to 0.3 % Sc added are between 150 to 160 MPa (22 to 23 ksi) at 10 million cycles. This is identical to fatigue strengths for comparable 50 series alloys, and is inferior to the fatigue strength of 70 series alloys. Some studies suggest reduced fatigue strengths for certain aluminum-scandium alloys in comparison with similar conventional aluminum alloys.

Fracture toughness is another critical material parameter for fatigue life. This material property is related to the stress required to propagate a crack of a given size. The higher the fracture toughness, the larger the crack that is tolerable for a given stress, or alternately, the higher the stress for a certain crack size. Adding Sc to a 7010 alloy reduced fracture toughness to around 60% of the conventional alloy. This is a serious and significant reduction, implying that the allowable stress must be reduced by a comparable amount. Again, this trend is confirmed by other work cited in the literature. In some cases the fracture toughness of aluminum alloys with Sc added was only about 10% of that of comprable conventional alloys. This is a serious drawback in a material intended for a firearm.

I did not find any information on wear, friction characteristics and machinability of aluminum-scandium alloys.

The limited information available on aluminum-scandium alloys suggests that the primary advantages are the ability to weld higher strength alloys, and a possible improvement in corrosion resistance. There may be a small increase in both ultimate tensile and yield strength, but this is offset by a dramatic reduction in fracture toughness. At best fatigue strength is comparable with conventional alloys. To quote one source: "The average values of fatigue life parameters appear within a range of magnitudes common for many engineering Al-alloys produced by conventional techniques." (ref: A. Vinogradov et al, "Fatigue life of fine-grain Al-Mg-Sc alloys produced by equal-channel angular pressing," Matl. Sci. Eng. A, A346, 318 (2003)). I think that use of the aluminum-scandium alloys in firearms is an example of the "single property fallacy," in that the emphasis is on the small increase in ultimate tensile and yield strengths without considering the full range of applicable properties.

So I would not expect a 1911 with an aluminum-scandium frame to show any better service life than a Colt Commander with a forged 7075 frame. It would not surprise me if the aluminum-scandium frame actually proved to have a shorter service life, since the fatigue properties of certain of these alloys are inferior to those of conventional materials. For a revolver frame the aluminum-scandium alloys may allow a small decrease in weight, although this is likely to be offset by a reduced service life (an extremely lightweight 357 Magnum probably will not be shot much, so this is an acceptable trade).

Again, I may change my opinion if better data becomes available. At the moment I think that aluminum-scandium for firearms is mostly marketing."


When asking my friend a question, you need to be prepared for the answer. It's usually longer, more detailed and blunt than sometimes is expected or desired (LOL). In the 30+ years I've known him I have never found him to be materially wrong or prone to give bad info.

Dave

 

[Catshooter]

Very, very interesting. Thanks for answer. I actually understood it! That's a credit to his writting skills!


Cat

 

[bubbajoe45]

Interesting! I have an S&W Sc Commander. His comments, while well researched and presented, are caveated by the proprietary nature of S&W's alloy. Thus, it remains a possibility that S&W has addressed the Fracture Toughness issue and this is simply not available in the literature. I guess I'll cling to that. Maybe Clint Smith's idea of buying several of anything he really likes is a sound practice. thanks for the effort DaveT.

 

[Catshooter]

DaveT,

You mentioned that you've killed three Colt Commanders by shooting them. Care you to describe their lives? Round types, round count, etc?

Thanks.


Cat

 

[Dave T]

First one cracked at the dust cover on both sides at around 2500 rounds, most a handload duplicating 230 Ball. Second cracked at the slide stop cut out, the dust cover on one side and showed a hairline crack at the slide stop hole itself (it had been electroless nickeled) after approx 5000 rounds. The heaviest load shot in it was Fed HydraShok 230s (not +P). The third one cracked on both sides at the mag release and under the thumb safety. It digested the most rounds, about 6500, none of which were heavier than non +P factory.

Dave

 

[deuterij]

Very good information and agrees with everything I have heard about materials. In the oilfield, 4130 is common for good reason. Various Inconel grades (high nickel alloys) are used for non-magnetic, corrosion-resistant applications. Galling of 17-4PH is also well known in the oilfield. Some of these assembled 17-4PH parts (especially large diameter helical threads) seemed welded together when you tried to loosen them. Small bits of material would ball up and fill the space in the thread locking it up.

There was a forum thread about N-frame heat treating a while back. This materials information adds to that. Steel has many mechanical properties (beyond hardness or yield strength) with trade-offs between them. Fracture toughness is hugely important.

 

[H P Bushrod]

Interesting post. Thanks for sharing.

 

[Catshooter]

Thanks for the informative reply DaveT.

Makes me wonder about the life span of my aluminum framed Shorty .45.


Cat

 

[perpster]

DaveT, This is a great thread! Dare you ask your friend about MIM parts?

 

[bubbajoe45]

Thanks for the informative reply DaveT.

Makes me wonder about the life span of my aluminum framed Shorty .45.


Cat

Me too! I have 4 aluminum-framed .45 autos (Sig,kimber,para, & Smith (with Sc)). At most, one of them may have a little over a thousand rounds and I don't shoot +P. Also, thanks again for your efforts DaveT.

 

[Dave T]

My friend cracked the frame of an alloy framed Para Ord some years ago. We discussed alloy frames then as it was about the time I cracked my second or third Commander. His take was that the forged aluminum frames could be expected to digest from 5,000-7,000 rounds. He indorsed the idea that alloy framed guns were intended more for carry than digesting thousands of rounds for years. There is some design consideration there too. The 1911 frame was initially designed to be made of steel. It takes quite a beating which work hardens aluminum. A gun like a SIG, with a purpose built/designed alloy frame will probably hold up longer.

That's all paraphrasing his thoughts, but we discussed this subject (his and my cracked frames) over and over for several years. I'm confident about this being his take on the subject.

Dave

 

[CAJUNLAWYER]

I've only got two lightweights-a 317 and a 337. After reading what your friend had to say, I'm knida glad.
Were the 1970-80 era blued N frames made of that 4130 ?

 

[rayb]

?Sticky?

Please, maybe in the gunsmithing section

Thank you

Very well presented, informative post.

rayb

 

[Catshooter]

DaveT,

Your friends take on the dreaded MIM parts would be interesting.


Cat