Steel vs aluminum (alloy) . your pick

M

Mattj4867

New member
There is no debate that a steel frame is harder and stronger than an aluminum (alloy) frame. Most of us will never live long enough to see our guns "wear out." which do you prefer and which guns do you prefer that have that characteristic. I prefer steel because of my auto 5.
 
I don't know of many bolt, lever or pump rifles with aluminum receivers except 22s. The centerfire BLR comes to mind but the bolt locks into the barrel extension, receiver material is almost a non-issue. I'm sure there are others but I can't think of one at the moment. Auto 5 is a shotgun; whole different animal.
 
Nothing wrong with aluminum as long as the firearm was designed for it.

Battlefield Las Vegas says that some of their M4's are in excess of 200,000 rounds and that both the uppers and lowers are perfectly fine.
 
They are all 'alloys' , even steel is an alloy of iron and carbon .
Yes if a gun is designed for Al or Plastic properly it will do well.
Of course when " bean counters " are the designers things may fall apart ! MIM is a good example of that .
 
mete.....Of course when " bean counters " are the designers things may fall apart ! MIM is a good example of that .
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If you are referring to accountants as bean counters, being a CPA, I can guarantee that accountants do not make corporate decisions or design any products.
 
Diamond tires suck, and so do rubber drills
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That is seriously funny! And true!

As far as materials used in firearms, as long as the design accounts for the properties of those metals, no problem. I had a Sauer 205 years ago. Got rid of it because I am a M98 fanboy, but the rifle was well made and strong, and it shot well. The M16/M4/AR-15 platform has been around for half a century now, it seems stable. Design it right, it works. Cut corners or substitute improper materials, and it falls apart.
 
Being a guy who works with and loves metal (all of them) I would have to caution that a gun should have steel wherever stress is applied. The reason I say that is that I know that aluminum (any alloy) that is put under tension, compression, or twisting, no matter how slight or infrequently, will eventually fail. Steel can be engineered and built so that it never fails as long as it is used within is stress limits. Aluminum can't. That is not to say that aluminum can't be used in guns. It can. The AR platform is a good example of the use of aluminum in a stress free area of a gun. The lower doesn't absorb recoil, is not in a position to absorb any stress related to the operation of the gun. It is mearly mounted to the gun to hold the serial number and the magazine. Doing that it will likely last a good amount of time. Slides on semi-auto pistols are a stressed part and they have broken proving that they should be made from steel. The frames of feather weight revolvers that are made from aluminum have also failed - cracking where the barrel and frame are connected on the underside of that connection.(both S&W and Ruger have experienced this issue)
Aluminum parts on aircraft and race cars are replaced after a certain number of cycles to prevent catastrophic failures but, on occasion, catastrophic failures happen anyway. I don't believe that any gun manufacturers have instituted a cycle oriented replacement schedule yet so I am left to believe that they either believe the public won't own a gun long enough to fail or that they are not concerned that the public is smart enough to realize a failed aluminum part is grounds for a law suit that could cost them millions. It is, in my opinion, negligent to present a gun, knowing it could fail due to improper engineering, as anything trustworthy to use indefinitely.
As noted the above is my opinion. Take it for what it is worth to you.
 
Shootist, you sound like a metallurgist, or a blacksmith. Either way, I'm right there with you, except for one thing. Aluminum can be used in stressful environments as long as they are replaced after their fatigue life, like you said, OR they are kept below the maximum stress level on their S-N curve (a material property based upon strength, ductility, and molecular structure). The reason steel is "unfailable", along with titanium, is that for a given alloy, there is a theoretical value below which failure is 'impossible', at least due to fatigue loading. The reason this is so high is due to steel's much higher yield strength and different grain structure. However it does take the right kind/alloy/grain structure steel as lesser steels can fail just as easily as aluminum.

So as long as aluminum is kept below the fatigue life line of the S-N curve, it's fine. Now granted, this would take one knowing what the S-N curve looked like for their gun. This is why aluminum is used in "stress free" parts of the gun, but they can be used in higher stress areas with the right analysis. However if the stress level is high enough, obviously the fatigue life will be so short that an aluminum part would crack in even normal service, nevermind rough service and hard handling. At which point I think it would be reprehensible to use aluminum in such a part.

References:
School
S-N Curve (as a refresher to myself. School was a while ago.)
 
"...Steel vs aluminum..." There is no 'VS'. There is just one or the other. Engine blocks have been made out of cast AL for eons. The armour on the turret of a LAV and the entire hull of an M113 is Al too. Steel can be soft or hard too.
"...MIM is a good example of that..." Of what? There's nothing wrong with MIM parts. Ruger has built their entire business on investment cast parts.
 
Battlefield Las Vegas says that some of their M4's are in excess of 200,000 rounds and that both the uppers and lowers are perfectly fine.
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Kozak, interesting. I guess they worked on the quality since Battlefield 2. My M16 seemed to wear out, I'm guessing, the 50K-60K mark. It's accuracy was severely degraded so I upgraded to the L96A1 and never looked back. After perfecting shooting once with the L96A1 and then switching to the pistol, I was just as combat effective in a CQB as anyone with an M4.. with the added benefit of being able to snipe if that's what the tactical landscape dictated.

Platinum, thank you for the link to a very informative article. Saved me a google search!
 
The problem with aluminum is that there is no "fatigue/life line". The fatigue life depends on the number of cycles at any input level. For instance; race cars started using aluminum drive lines. They did so to lower the weight and rotating mass. They knew that the shafts wold fail at some point and replace the shafts after a certain number of runs. Between runs they inspect for "premature failure indications". Now you can buy aluminum drive lines for your street car. Most people don't give there drive lines a second thought after installing them. The aluminum shafts will fail even if you never do anything more radical than driving to and from the grocery store once a week. The first time any torque is applied the process begins. Every time even 1 inch pound of torque is applied the process continues. There is no load, even below its minimum elastic deformation load, that doesn't add to the process.
This is completely different from steel or even iron. These metals have a minimum load that causes fatigue that is beyond its minimum elastic deformation load. '

Think of it this way:
We have a room with an inert atmosphere (say Argon) and zero humidity.
We have two metal plates that are 18 inches long 1/4 inch thick and 7 inches wide.
Plate A is made of mild steel and plate B is made of aluminum.
The two plates are suspended across frictionless rollers 3 inches from the ends.
The environment stays exactly the same except for the temperature that cycles in a sine wave pattern from 35F to 95F and back to 35F every 24 hours.
Other than the thermal loads, which are in no way extreme, the only other load is that of gravity.
Given enough cycles the aluminum will fatigue and fracture while the steel will eventually bend a bit.
 
I will agree with your thought experiment, but how many cycles will it take to fail the aluminum bar? I agree that it will fail "some time", but the number of cycles it would take, make your thought experiment just that: a theoretical experiment. My apologies if I used the term incorrectly, but the "line" for aluminum is not the same as the "line" for steel; we agree there.

I get what you are saying, there is no minimum level that aluminum can stay under and live forever because it depends solely on cycles, but as long as you keep the stress per cycle under the allowable stress according to your S-N curve for the useful lifetime of whatever part/thing is made of aluminum you would never see aluminum fail. If this is used in a car, depending on the analysis, the aluminum driveshaft may not be what sets the lifetime. If the part is used on a firearm, the barrel may become unusable before the aluminum part fails, or the stock will fall apart, etc.. Whilst both scenarios are of items that can be rebuilt, it may or may not be an item that you would even rebuild if another major system failed. So using aluminum in targeted use is completely fine, so long as it is designed appropriately.

Edit: just realized that this in the art of bolt/lever/pump. My apologies for taking this off track.
 
I have aluminum cylinders for my paintball guns that have had hundreds of cycles g being filled and emptied. I have paintball guns with hundreds of thousands of cycles. What more do you want?

in engineering- everything is a compromise.
 
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