What do you know about MIM


May 29, 2011, 05:53 PM
Seemed to me I was hi-jacking a 1911 thread talking about MIM parts. I'd really like to find out more. What can you tell me about MIM.

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May 29, 2011, 05:55 PM

May 29, 2011, 05:59 PM
How about this: google is your friend...


May 29, 2011, 06:02 PM
The problem with MIM in handguns is the motivation behind its use. It is not there to make the gun better. It is there to make the gun cheaper. Like any process, forged, cast etc.... there are good and there are bad parts produced using these processes. So the real question is always what is the quality of the parts in any given gun at any given time.

Kimber was the first to really experiment with MIM and in the beginning did a excellent job with it. Problems came up when they continued to squeeze more and more pennies out of the process. They reduced the quality to the point of failure. So the MIM in an early Kimber is OK while a one from 2005 might not be while a 2011 one might be ok.

Typically when MIM fails it fails early and catastrophically. For example a thumb safety will shear off the frame. It will come off into 2 pieces.

IMHO this is where MIM parts get their bad rap.

May 29, 2011, 06:07 PM
Did the google thing, surfed the websites.What I'm askin is : Has anyone actually had a MIM part fail on them. Seen them wear excessively. I'm looking for real world info, not what some company has to say.
Wikipedia is notorious for bad info.

May 29, 2011, 06:12 PM
If you use the search function, there have been many discussions of MIM parts here, including accounts of failure/wear/etc.

May 29, 2011, 06:12 PM
They use MIM on the Space Shuttle

Kendal Black
May 29, 2011, 06:19 PM
I think it is fine if it's done right. But isn't that the case with everything? When MIM parts first began showing up in firearms some people were nervous about them. Events have not borne out their concerns.

MIM parts can fail, of course. So can forged and machined parts. Does anyone have a solid comparison of the failure rates of both?

I don't worry about MIM, reasoning that if a part is correctly designed and made by whatever method it has the strength and durability to do what it needs to do--that's just engineering.

I once had a traditionally machined auto transmission part go spung way out in the Mojave Desert, leaving me stopped and stranded; turned out to be a flaw in the forging. Heh. So the old way has its failings, too...

Another look at the matter: http://www.stiguns.com/FAQ-MIM.php

Kendal Black
May 29, 2011, 06:21 PM
[...] What I'm askin is : Has anyone actually had a MIM part fail on them. Seen them wear excessively. I'm looking for real world info, not what some company has to say.

They've worked fine for me. Haven't seen a problem.

May 29, 2011, 06:36 PM
here we go again

May 29, 2011, 06:44 PM
Im With rellascout!

They work sometimes...they break sometimes! :(

No matter who made the gun....no matter how much you paid for it!

May 29, 2011, 07:10 PM
i'm microwaving a bag of pop secret. such a unique topic warrants it.... :eek:

May 29, 2011, 07:45 PM
I just got back from shooting. Ran 50 rounds as hard as I could push them through 4 mags.Brings me to an even 1000 in 2 months. No failures, so I guess I won't worry about anything breaking. Thank you for your input, and your patience.

P.S. used those links, guess they say it all. Thanks again.

May 29, 2011, 07:54 PM
This is one of those things that people agonize over instead of looking at what's really important.

Plastic and aluminum are much weaker than a decent quality steel MIM part, yet we all know that if a designer knows how to make use of these two materials in a manner that doesn't overstress them they can provide lifetimes of service.

Rather than trying to learn all about firearm design, metallurgy and manufacturing techniques, it's much more productive to learn gun companies. Which ones are known for being dedicated to putting out a quality product? Which ones have an excellent reputation for customer service and for backing their products 100%?

Pick a product with a good reputation for durabilty and function from a company with a good reputation and don't get down into the weeds of trying to learn the intricate details of metallurgy and gun design (unless that's something that really interests you).

You'll end up with a product that will work from a company that will make it right in the unlikely event that you have a problem.

You'll be WAY better off than the guy who bought a gun made using all the "right" techniques and materials from a company that doesn't have a good reputation for making products that work and that isn't known for making a serious effort to keep their customers happy when things go wrong.

May 29, 2011, 10:34 PM
and thanks for going to the trouble!

May 30, 2011, 12:01 AM
Back in the day, you forged things to make them stronger, then machined them to make them accurate, overbuilt everything you could because you didn't have the tools to figure out what's really important, tested the hell out of it, fixed the crap you missed, and then a couple of years later changed a couple of troublesome parts. This got you to a decent design if the basic design was good.

Now, you design, do the finite element analysis, figure out where it's going to break, fix the design, do a Failure Mode Effects Analysis and fix the design some more, knock as much cost out of it as possible, because if you don't a competitor will, and when you are ready, build tooling, go to production, ship product. It damn well better be right the first time.

MiM, plastic, carbon fiber - anything really is just a tool to get where you need to be cost and quality wise. Hell High Point makes effective functional guns out of plastic and zinc castings and the things are well made - not esthetically pleasing but reliably go boom when needed and are strong and way durable for the buck. MiM is important because things that were once machined can now be cast, reducing cost hugely, and in the last 100 years metallurgy has advanced hugely - so what MiM could not have done even 20 years ago is now possible.

And if someone makes a part, with whatever process using whichever material, and that part fails due to design, the fault lies not with the process or material, but with the engineer.

May 30, 2011, 02:43 AM
They use MIM on the Space Shuttle

Yeah, and we all know how well that worked out,,,twice,,,

May 30, 2011, 02:44 AM
And if someone makes a part, with whatever process using whichever material, and that part fails due to design, the fault lies not with the process or material, but with the engineer.Bingo.

Put your research effort on finding out who puts a premium on building reliable, durable products and who stands behind their products 100% and buy from them. Let them worry about the technical details and you can take comfort in relying on their reputation.

It's a sound strategy. And, frankly, for most of us it's the only reasonable strategy. Seeing us argue about forged vs cast vs MIM as if that's the primary deciding factor in the strength of a part must be highly amusing to people who really understand metallurgy.

The first step is realizing that "steel" is not just one material. There are something like 3 to 12 major classifications of types of steels and literally thousands of different steel alloys--certainly more than 4500. All of them have different properties. And there are many different materials (at least 16) that are commonly used to alloy steels. Altering the concentration of these materials in the steel by tiny fractions of a percentage point can dramatically affect the properties of the resulting alloys regardless of how the final part is formed.

The second step is understanding that even if we focus on just one alloy, the pertinent properties of steel alloys (tensile strength, elongation, hardness, etc.) are highly dependent on the heat treatment.

Third, if we compare parts that aren't completely identical, then that adds another level of complexity since we're now evaluating the durability/strength of the parts design itself in addition to all the other variables.

IF, we could find two: Identical parts
Made from identical steel alloys
With identical attention to quality control
And identical attention to proper manufacturing processes
And which have identical heat treatmentsTHEN and ONLY then could we have a chance of making an intelligent/accurate general comment about the relative durability of the two parts based exclusively on the method used to form the part.

There are numerous factors which contribute to the strength of the final part. The manufacturing method is just ONE of those factors and isn't really even high on the list of things that are likely to affect the final result. Trying to make an assessment of durability/strength purely on the basis of the manufacturing method of one gun (or part) is ridiculous.

May 30, 2011, 03:01 AM
Yeah, and we all know how well that worked out,,,twice,,,

ceramic tiles were what failed on the space shuttle, not MIM parts lol

May 30, 2011, 07:33 AM
Good MIM can be very good. Excellent, actually. Bad MIM is junk. The problem isn't in the process, but rather in the execution. If the part has voids in it, it'll fail. The other problem is that it's often impossible to spot a problem until it does fail without magnafluxing it...which would defeat the purpose of making the gun cheaper to produce.

I'd rather have good MIM in a gun than bad steel. I have an older Colt 91A1 with the original MIM sear and disconnect in it. The gun has endured something approaching 200,000 rounds...through one slide/frame refitting...and on its third barrel.

On another identical gun with a nearly identical round count, I replaced the disconnect at 75,000 rounds when it was refitted. It wasn't causing a problem. It just looked a bit worn, and I wanted to nip any impending problem in the bud. The sear is still on duty.

I had a guy come to me with a Colt 91A1, and asked me to replace the sear and disconnect. I did, and used the OEM parts in a test. I laid the sear on an anvil and hit it with a hammer...pretty hard. It didn't break, and when I installed it in a gun, the gun functioned...although the trigger pull was a little rough.

I've also seen the same parts fail with low round counts in other manufacturer's guns. Colt has apparently found a vendor that knows how to produce good MIM.

Generally speaking, if an MIM part is going to fail, it'll do it early. If the part lasts for a thousand cycles, it'll likely last for 50,000 or more. MIM parts that don't undergo impact forces generally do better than those that do. MIM parts with heavy cross-sections fare better than those with thin cross-sections. MIM hammers make me a little nervous. Impact and small hooks are potential trouble spots.

One thing that I do know. Love it or hate it...it's here to stay.

May 30, 2011, 11:06 AM
Actually, on the first shuttle failure the "O"ring seal between the booster parts failed allowing hot gasses to escape igniting the main fuel tank.
The second failure happened on liftoff when foam insulation came off during liftoff, damaging the ceramic tiles allowing heat from re-entry to cause catastrophic failure.
The EPA forced NASA to quit using CFC's in the foam insulation on the main fuel tank making it weaker and subject to failure. On almost every launch since then a piece of foam nas come off. Unintended consequences of overzealous regulation.
Exactly what this has to do with the OP, I have no idea.

May 30, 2011, 11:52 AM
I'm not a big fan of MIM just for aesthetic reasons and pride of ownership (I like guns that have some handwork in them). But, as 1911Tuner put it far better than I could, there's nothing wrong with the technique if done right.

What really amazes me, though, is the litany of complaints about this technology from people who act like it had just been invented and foisted on the firearms world. Colt used sintered parts (a closely related metal-forming technique involving powder metal) for their lockwork since the early 70s, and nobody complains about those. You ever see a Trooper Mark III? It has a sintered hammer and trigger (and possibly more).

May 30, 2011, 02:53 PM
Was shooting a friends GSG 1911 in .22. The barrel bushing is a MIM part and the part that retains the spring broke clean off after about 1000 rounds and the spring went downrange. I dont like MIM parts for things like that or thumb safeties, etc. Those parts are usually thin weak and feel like low quality pieces. Its all due to the bean counters push mass market products. There are good MIM parts, but they are few and far between.

evan price
May 31, 2011, 12:47 AM
In an application properly engineered for it, well-crafted MIM parts work fine. They require less finishing than a bar-stock part when manufacturing. They can be made to very close tolerances and densities. They work best in parts with less imapct and sheer forces. For example, I wouldn't want a MIM knife blade but a MIM knife frame would probably be fine. I've never had a MIM gun part break but I have seen broken MIM parts in other applications. My personal preference is for bar stock parts but when not properly heat treated they will fail prematurely too.

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