Alluminum Alloy Debate

for Alex Johnson

I too have a Kimber Ultra (series) with the nice aluminum frame and it makes a wonderful carry gun. And Yes, Kimber says they have tested their frames to 20,000 rounds with no appreciable wear.

That statement about no appreciable wear is very specific and also very vague. They fail to mention just what type of rounds they were firing (full power, reduced power, or what) and the statement ONLY concerns wear, nothing else.

My Ultra broke at a few hundred shy of 10,000 rounds. Stress fractures formed just in front of the slide stop holes on the dust hood of the frame. So, sure my frame was still almost at tight with the slide as when I bought it (no appreciable wear), but after 9600 full power rounds, the frame cracked.
 
I have seen two cracked P220 frames.

Of course, I've also seen numerous steel 1911 frames with cracks...

Never seen a cracked Ruger though.......hmmm........
 
There are a few items that haven't been covered yet.

Fatigue life:

In steel and titanium alloys, the fatigue life is assumed to be infinite if the stress levels are kept below %50 of their yield strength. If the design doesn't have an adequate safety factor, it will eventually fail.

The same cannot be said for aluminum alloys, aluminum has a finite fatigue life. It will eventually fail. When aluminum fails can vary greatly depending on the alloy and temper, and design.

Abrasivness:

Depends on the molecular structure of the alloy. Aluminum and titanium are much more abrasive than steel. Anodizing is essentially an oxide coating of aluminum. They also make sandpaper out of aluminum oxide. titanium dioxide is the primary component of white sand. Under the same circumstances, a steel slide on a steel frame will not need "tightening up" as soon as a comparable aluminum or titanium part, even with proper lubrication.

A few other items:

Carbon steel is redundant. If the steel doesn't have carbon, we call it iron.

Stainless steel is basically steel with a high chromium/nickel content. This makes it more corrosion resistant and can mess with the magnetic properties.

Melting temperature has absolutely nothing to do with tensile strength or hardness, which by the way are directly proportional.

Titanium is not a wonder metal. Sure, when comparing it to ASTM A36 steel, it's got an awesome strength to weight ratio. When comparing it to 4140 or 4340, it's not so hot anymore. Tensile strength of Ti is between (from memory) 90kpsi and 140kpsi depending on the alloy, and it's probably one of the worst metals on earth to machine. It's advantage of corrosion resistance at standard temperature and pressure is negated at the high temperatures and pressures that are common in firearms, it doesn't even need oxygen to corrode, nitrogen will do just fine, and you end up with a titanium nitride coating, which is extremely hard but very brittle. Add in the abrasivness, and titanium is just an all around bad choice for use in firearms. However, it's Great for use in dental implants, but that's another thread on a different board.

Conclusion:

There are no bad metals, just bad designs and applications of metals. I don't deal much in polymers, so I'll just use plastic for grip panels.
 
Reviving this old thread just to mention how great it is to be able to hear such informative debates. The breadth and depth of knowledge shown is impressive.
 
Those Ruger Semi-Auto's may be "ugly" to some...but regardless of whatever kind of alloy they use...I can't see my P94 EVER wearing out!:cool: my grandkids will end up shooting that gun.
Tony.
 
Like my best friend Forrest Gump once said, "Guns are like a box of chocolates, you never know what you are gonna get". Or was he talking about life???:)

All have their good and bad points. No two guns are exactly alike. You can have two identical guns and one may crack after 10k rounds, while the other go all the way to 50k rounds before cracking. Even with each brand, type and model or frame construction, each one will not be exactly the same and will respond differently.

Of the choices for frame construction, the stainless steel will be the best, being steel and extremely corrosion resistant. The carbon steel will probably come next, followed by IMO the polymer and alloy frame equally. But again, they are all going to be different. Treatment, caring, cleaning, etc, all play a factor on its lifespan. Only time will tell. All we can do is look at the average estimate of lifespan for each frame type construction.

As been said, there have been steel framed pistols that has been known or seen to crack. Then I have also heard not from Sig, but Sig owners, that some have sworn to have fired over 20k rounds on their P220 or other classic Sigs with Al alloy frames with no problems. I guess durability wise, the Al alloy would probably be the worse, but only because they scratch and gouge easily. I have Sigs and have experienced it. But they shoot and feel perfectly. Not too heavy and very nice to shoot. Polymer frames are nice and light, but don't like the top heaviness about them. Once damaged, pretty much impossible to repair. Carbon steel is strong and feels ok though a bit heavy, but very rust vulnerable. Stainless steel gives the best durability with strength and corrosion resistance, and easy to buff out scratches. But it too has a trade off. It is very heavy. The P220ST stainless is almost 3/4-1lb heavier than the regular carbon steel/Al alloy framed P220. Each has a trade off, but depends on your use and purpose. I don't like polymer frames at all unless for carrying. Polymer and Al alloy framed guns are great for carry as duty weapon being light and rust resistant. For home defense and just target shooting, anything will do as long as you take care of it. Since I am not a COP and have no purpose for a duty weapon for carrying around, polymer is out of the question for me since i don't like them. Frame-wise my first choice would be stainless of course. Second is aluminum alloy if it is a Sig. It's worth the hastle of Al frames if it's a Sig, cause they make awesome guns and I love Sigs more than any guns. carbon steel is next, but make sure it has a good coat like hard chrome. It all comes down to purpose and use....
 
I'm sure that steel is harder than aluminum, and probably will wear longer. I think that with todays modern metallurgy aluminums are far better than they were even 15 years ago. I'm not sure if this helps but my only pistol S&W910 is alloy framed, and there is no more wear than there was on the rails at 300rds.
( Ive shot close to 4000rds of ammo through the gun). Or at least none discernable with the naked eye. It still shoots to the point of aim and I can manage 2.5inch groups at 25yards off a rest. If your not going to use the gun as a competion gun and shoot thousands of round every week , Who cares??:)
 
As a former bicycle mechanic, people would ask what's the best frame material? (Titanium, carbon fiber, chrome moly steel, aluminum, metal matrix, magnisium, all in a variety of grades) The easy answer was titanium, but any generalization you could make about a frame material was easily refuted with one example or another of a brand that defies the experts, like the super light, super stiff 6061 aluminum Cannondale. So you took it on a case by case basis.

So too with guns. You could get excellent life from nearly any material if designed right. You will see more worn out steel 1911 frames than alloy Ruger frames. Ruger knew more about making aluminum pistols in the 1980's than Colt did about steel in the 1900's. Polymers and composites have been in use in sporting goods for 30 years; the polymer guns of today are just catching up with other industries.

The design dictates the material. If that is done correctly, the material is not an issue. A magnesium 1911 is just as bad an idea as a steel framed glock.

Ultimately, plastic may be the best choice for the current preferences in auto design, but it would be nearly impossible to make a P7 or P9S with anything but steel frames. So when people change their minds again about what they want in an auto, the prefered material will change too.
 
BEDLAMITE, I wasn't aware that white sand had titanium dioxide in it (and you may be right). I know sand is primarily sililcon dioxide and that titanium dioxide is placed in white paint for the color it imparts. Tell me more about TiO2.
 
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