Alluminum Alloy Debate

Q

Quantum Singularity

New member
I waited for this thread to be moved from revolver to semi-auto, but since the moderators didn't do it I reposted it here where it was meant to be. Moderators: feel free to close the one in the "revolvers" forum.

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I don't know much about the properties of metals, but I want opinions from those who do know more than me (you guys). Is it true that most alluminum alloy frames have a life of 10,000 rounds? I keep hearing this rumor but have no way to check it out for accuracy.

Also, I am interested in opinions on the durability of the following gun frames:

Stainless Steel
Carbon Steel
Polymer
Aluminum alloy

From what I read, the polymer and steel frames are the most durable, but I would appreciate other opinions as well.....
 
I don't know about the 10,000 round life expectancy, supposedly my Kimber Ultra carry has been tested to 20,000 rounds with no appreciable wear. Aluminum alloys have improved considerbly in the last 10-15 years. I just bought a new 80's vintage Charter Arms snub with an aluminum frame on it, but I wouldn't trust it to be as durable as the new generation aluminum frame pistols, the alloys would likely be considerably different. I've worked as an engineer at two different companies and in both of them I have had some experience with some of the different alloys of aluminum. The one that sticks in my mind the most is what I belive was designated 7075 some call it fortal. This stuff was amazing, I used it extensively in call outs for parts that had to be extremely light, yet very strong. It had a reputation as being more durable than standard 1020 cold rolled steel as far as it's ability to resist dents went, it had a certain springiness to it that steel doesn't. I also know that it can be surface hardened (by a process that I'm not familiar with) into the 60's on the rockwell scale. In short, some aluminum alloys can be made into very durable pistols, as long as it is chosen for appropriate parts.
 
I think that this question is easily ans'd. Tinsel strength between steel, aluminum, brass etc is considerable. If you consider the melting point of alloy and brass is around 800 degrees and if my memory serves steel (4140) is around 1500 degrees. This should tell you something. Now consider, alloy frame, steel slide. The slide is of harder materail will last longer. The wearing of the slide on the reveiver will create loosness in the operation and wear the receiver out long before the slide. l

I have trained Fed. officers with the alloy stuff and as a training vehicle they didn't last long. I am from the old school, have built 45's (accurized) on the alloy frames and the aloy's always came back needing tuining and tightning.

HJN
 
Right On Harley,

I always figured the alloy frames were for carrying alot and shooting but little.

The place that I got to on light firearms is that the ammunition in a fully loaded pistol makes a firearms which is only a few ounces lighter, not seem very much lighter. Does that make sense? IOW, a pistol which is approximately 32 Oz, loaded with 7-8 .45ACPs is not much heavier than a 28 ounce Pistol with 7-8 .45 ACPs. Even a polymer like a Glock or Glock Clone like the H&K USP when loaded is still heavy to carry.

Now a .38 spl. is light but.......Ah...well it's light :).

PigPen
 
"If you consider the melting point of alloy and brass is around 800 degrees and if my memory serves steel (4140) is around 1500 degrees. This should tell you something." I'm considering a compact 1911 in steel vs alloy and am tending towards steel for stength, balance, and shootability, but I'm not sure what this is supposed to tell me. Are you attempting to correlate some important firearm property of the metal with melting point? I doubt that correlation exists.
 
My reference to the melting point of metal is to present the tensil strength of the various metals. It would seem reasonable, to me, that if brass and aluminum will melt at a lower degree of heat than steel this tells me that it is not as strong as the steel.

Rockwell hardness of the various metals would indicate the degree of wear it would endure. In my opinion and the final analysis, steel is harder and will wear less than the Alloy metal.

HJN
 
Too much variability of materials, workmanship, and design involved too?

No doubt in my mind the alloy framed Rugers are stronger than some forged steel pistols out there. The newer cast frame BHPs are better than some of the older forged frames too.
 
Harley, I think you should recheck your data. 4140 does not melt at anywhere close to 1500 degrees. Most steels melt closer to the 3000 mark than anything. Cast iron still takes something around 2200 to acheive pouring stage. Aside from that maybe their is some basis for melting point versis tensile strength, but I'm not too sure on that either. Gold has a relatively high melting point getting pretty close to 1900 degrees but I wouldn't want to use that for any working parts (cost aside). On the other hand, aluminum in some of it's newer alloys is very durable with a fairly low melting point. Newer aluminum alloys when they are surface hardened resist wear quite well (certainly better than un-heat treated tool steel) and are considerably better in both weight and corrosion resistant attributes. On the other hand, titanium beats them all as far as durability goes, though it's still heavier than aluminum. Unfortunately it too has it drawbacks such as being unsuitable for many working parts; as well as the barrel and it's a bear to machine to boot. Everything is a trade off in the end and the end question has to be what is the products intended purpose. For the casual consumer that simply wants a gun that is easy to carry and durable enough to meet practice requirements the alternatives to steel are out their and perfectly satisfactory. For the gun that is going to be shot a lot more than the rest of the pack than high quality steel frames, or some other space age material are the answer.
 
Polymer will most likely give the longest life IMO.

As for the life of alloy vs steel. . .

Look at pistols that are considered "durable" by today's standards. The M92 is an alloy frame and by today's theories is durable. The Sig P220 family is on an aluminum alloy frame and considered durable. The Ruger P85/89/91/90/93/94 are investment cast alloy framed also.

Now looking at the 1911 alloys, the common heard phrase is "carried often shot little". Perhaps the 1911 design puts too much stress on the alloy because of its design. Also consider that the alloy used in the original lightweight 1911s is not the same quality alloy that is being used now. I have not heard of many *modern* 1911 alloy variants being shoot to pieces with *normal* range work.

The defintion of *normal* is debatable though. Some folks shoot 500 rounds a year, some folks shoot 500 rounds a week. Everything has a "life expectancy" and a consumer should pick their choice based upon their intended uses. If I was going to run say 2000 rounds a month through a pistol, I'd pick a polymer/high quality steel frame first.

Derek
 
I was going to ask a (kinda same) question about my 9mm mak made by FEG Hungary, it has an aluminum alloy frame and I was wondering about the wear also.
If anyone knows if it is one of the better alloys I would sure like to know.
Reading all the posts it seems to me that a good grease on all the points where the slide comes in contact with the frame would be something that would help any wear problems, good or bad alloy. Just my .02
 
I have to agree with the carry a lot shoot small aluminun frame 1911 type pistols as I recall I read Jeff Cooper said or wrote that about the STAR PD pistol, so I will have to side with him on that issue.
As far as the new aluminun frame pistols I had a Ruger P-85
and shot about 6000 rounds without a failure or noticeable wear.
Some polymer pistols have steel or 7075 aluminum inserts
in the bearing surfaces.IMHO the aluminum will wear faster than steel but a hardcoat anodizing and appropiate lubrication should make the pistol last for a long time
unless it is used for competition. Also the design of the pistol and manufacturing quality controls will dictate how long it will last regardless of the material.
 
Gentleman,

The aluminium used in todays pistols are of two classifications, T6 6061 and 7075. Most of the newer pistols are made of 7075 alloy as it has a higher tensile strenth than 6061. For those of you that doubt its toughness, these are the same alloys used for fighter and passenger jet parts. The tensile strenth of T6 6061 is around 60,000 psi. The tensile of 7075 is around 70-75,000 psi. This compares favorably to the steel used in most guns (4140) which is about 80,000 psi in a heat treated state.

4140 is a high carbon steel which can be heat treated to different strenths. Most gun steel 4140 is heat treated at 1500-1600 degrees, then annealed to reduce the hardness of the metal, as the harder the metal is, the more brittle it becomes. The annealing process bring down the hardness a bit and reduces it brittelness, making it more useful for gunparts.

Most of todays aluminum frames are anodized. This is a chemical plating process that imparts a thin skin, usually less than half of a thousanth(.0005)thick which is much harder and durable than the aluminum itself. This anodizing process can be done in just about any color, even clear as many of the frames of today are.

The aluminum frames of today have come along way as compared to the aluminum frames of 10-20 years ago. New coating processes and heat treaments make them more practical than ever before. I have personally shot over 15,000 rounds thru a Taurus PT99 and over 10,000 thru a PT101 without a hitch. About the only bad thing I can say about the Taurus was that some of the anodizing wore off of it after coming in and out of my holster so many times. I shot steel plates with it, so it has seen alot of action. However, my government model .45 which has a steel frame did not fare any better.
Personally, I would not hesitate to buy an aluminum framed handgun. In fact,I have several. They are exellent guns.

If there were any doubt as to their toughness , the more popular models such as the Rugers, the Sigs, Taurus's, the ParaOrdances would simply cease to be. As everyone here can tell, that is simply not the case. If aluminum frames were as delicate as SOME people claim them to be they would eventually be phased out, instead they become more popular each year.

Sure ...any gun can wear out, even a steel framed one. But how many people do you know have actually worn out a gun by shooting it ? I dare say ....probably not many here have done so.
 
Since we are talking about metalorgy, let's define a few terms as related to carbon steel:

Annealing: A thermal cycle involving heating to, and holding at a suitable temperature, and then cooling at a suitable rate, for such purposes as reducing hardness, improving machinability, facilitating cold working, producing a desired microstructure, or obtainging a desired mechanical or other properties.

Normalizing: A thermal treatment consisting of heating to a suitable temperature above the transformation range and then cooling in still air. Usually employed to improve toughness or machinability, or as a preperation for further heat treatment.

Quenching and Tempering: A thermal process used to increase the hardness and strength of steel. It consistes of austenizing, then cooling at a rate sufficient to achieve partial or complete transformation to martensite. Tempering should follow immediately, and involves reheating to a temperature below the tranfomation range and then cooling at any rate desired. Tempering improves ductility and toughness, but reduces the quenched hardness by an amount determined by the tempering temperature used.

Typical examples of heat treatment of 4140 for a 1" round:

Annealed, heat to 1500F, furnace cooled 20F per hour to 1230F, cooled in air. Tensile strength (TS)= 95000 psi, Yield Strength (YS)= 60500 psi

Normalized, heated to 1600F, cooled in air. TS = 148000 psi, YS = 95000 psi

Quenched and tempered, heat to 1550F and quench in oil, reheat to 1000F and air cool. TS = 156000 psi, YS = 143000 psi

Now a little information about Aluminum alloys:

6061 is a precipitation hardenable alloy. Typical heat treatments are T4, T451, T6, and T651. Typical strengths for T6 are TS = 45000 psi and YS = 40000 psi.

7075 is a heat treatable alloy. Typical heat treats are T6, T62, T73, and T76. Typical properties of T6 and T651 are TS = 83000 psi and YS = 73000 psi.

The Kimber web page indicates that they use Al 7075 for their frames. While it is good material, it is not as strong as 4140. Will an aluminum framed gun last as long as a steel framed gun? Probably not. But understand this, the length of time required to make the AL frame gun fail may be your lifetime.
 
Durn guys! Outstanding debate! Very instructive! This is why I prefer this forum! I have read, on a Sig page, that the factory claims to have some .40 Cal. Sig 229's that have been shot between 200,000 and 300,000 rounds with no appreciable (?) wear.
 
Durn guys! Outstanding debate! Very instructive! This is why I prefer this forum! I have read, on a Sig page, that the factory claims to have some .40 Cal. Sig 229's that have been shot between 200,000 and 300,000 rounds with no appreciable (?) wear.
Click to expand...

I wouldn't put much faith in Sig's (factory) claim without first seen documentation that backs it up. This just doesn't sound feasible (that many rounds with NO APPRECIABLE WEAR). Was there a way to check the factory's claim (validity) in that site? If possible, could you share the site address with us?
 
Alloy Sigs(Beretta?)and plastic Glocks, use steel inserts in their frames. These blocks take the recoil impact, and the impacts from locking/unlocking, and spread that force over a dramatically greater surface area of the frame. The LW 1911s impart that force onto a small slide stop pin, held by two holes on either side of an alloy frame, and onto a small U-shaped lip at the inner rear of the dust cover. I believe there is a dramatic difference there between the two.

The fore and aft movement of the steel slide over the frame's rails apparently does not cause much wear. IIRC, Glock only re-inforced the 17's rails with steel after some slides parted company with their frames in Federal(DEA?) trials. (Something to do with how they were squeezed when crushed under the weight of a car?) The CZ-100 has NO such inserts at all, though the rails would definitely be classed as 'full-length'. Ditto that of the Ruger P97, which has thick, square and un-reinforced rails.
 
i believe a Beretta 92's aluminum alloy frame is supposed to go at least 70,000 rounds but people have taken them past 100,000.
 
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